With the rapid development of new social and economic structures, commonly referred to as 'information society' and 'knowledge-based economy', modern economic sciences and other social disciplines have faced an entirely new set of cognitive and implementation challenges. The new rules have exerted their impact in practically all of the previously used notions, methods, techniques and algorithms of conduct, both those applied in analytical studies and in practical implementations, to the point that it may reasonably be assumed that the modern sciences are in need of an urgent revision and reinterpretation of the way they perceive the material and symbolic realities, and their understanding of changes in the established forms of social or economic activities. The focus of research presented herein is placed on a promising though probably inadequately analysed concept of the real cost of information acquisition from the third-party sources, i.e. from actors operating under the changed context of information society and knowledge-based economy. This concept represents the main research problem. The first stage of research involved verification of a thesis that, under the changed conditions of information society and knowledge-based economy, the established cost accounting principles need to be redesigned to include a cognitively and methodologically correct representation of the real cost of information acquisition from third-party sources. The second research thesis was formulated as follows: the best fundament for the above redesign is the welfare economics, particularly the associated concept of transaction cost economics, supported by the concept of alternative and social costs. The above two theses were further elaborated into four research hypotheses, formulated as follows: Hypothesis 1. The established forms of costing and cost account sufficient enough to provide proper identification and calculation of the real cost of information acquired from third-party sources, i.e. from actors operating under the changed context of information society and knowledge-based economy. Hypothesis 2. The traditional cost accounting models are possible to extend to include the representation of other costing categories. Hypothesis 3. Types of cost currently unrepresented in cost accounting models should be included in the examination of the real cost of information acquired from third-party sources, i.e. from actors operating under the changed context of information society and knowledge-based economy. Hypothesis 4. The new category of cost, i.e. the real cost of information acquired under the changed context of information society and knowledge-based economy, represent a significant portion of the real cost of such undertakings? The fundamental intention behind this research was not to examine the utility of an extended account of cost, as it seems an obvious conclusion and requires no proof. From the viewpoint of utility for decision-making applications, it may safely be assumed that better designs (i.e. more accurate and detailed representations of real costs) will offer better results. The author of this work was more interested in obtaining a confirmation for the need to introduce such extensions, since it would require a more or less radical departure from the established solutions. The changed conditions brought about by the rise of information society and knowledge-based economy are clearly manifested in the increased demand for information, including that from external sources. Moreover, the acquisition of the latter will naturally generate a new category of costs. The principal intention behind this research was to place due emphasis on the significance of cost associated with the acquisition of third-party information in the changed context of information society and knowledge-based economy, both for cognitive purposes and for detailed applications in the real economy. That defined scope of research was faced with two major types of challenge, namely: •• the concept of gratuitous information and the paradox of pricing for virtual products, typically associated with Internet distribution and virtual economies, and included in model analyses, •• traditional limitations of the microeconomic cost accounting, which tend to reduce the role of such categories as: the transaction costs, the alternative costs, and the various manifestations of social costs. Proper understanding and overcoming of the above challenges was the real moving force behind this research. Being well-aware of their existence and potential impact, the author formulated the main research problem - the identification and evaluation of potential for the assessment of the real costs of information acquired under the changed context of information society and knowledge-based economy. The analyses were performed on a sample of economic entities, including not only enterprises, but also other actors involved in economic activities. Although the latter typically operate on different sets of criteria, they are - nonetheless - expected to display a rational approach to the utilisation of rare economic resources. The first research thesis, postulating the necessity of extending the established cost accounting to include proper (cognitively and methodologically accurate) representation of the real cost incurred in the acquisition of information from third-party sources, seems fairly obvious. The scope of this author's research growing role of information in nearly every aspect of human operation and civilizational development down to cognitive and practical conclusions related to rational management and utilisation of rare economic resources assigned for activities associated with the acquisition of information. In the light of the above arguments and the associated evidence - in the form of factual observations and theoretical explorations - the first research thesis may be considered valid and proven. The second research thesis postulated that any such an extension of the cost account to include the real cost of information acquisition may be based on the principles of welfare economics, particularly the associated concept of transaction cost economics, supported by the concept of alternative and social costs. Verification of this thesis required a thorough review and critical evaluation of professional literature, with strong emphasis on cognitive utility and implementation potential of the already published findings and research observations. This author's research provides a lot of general and detailed conclusions and arguments in favour of the second thesis, attesting to the correct and cohesive form of the statement. In the light of the above, the second research thesis may also be regarded as valid and proven. Further elaborations of the first and second thesis came in the form of four research hypotheses, which were then subject to verification. The first hypothesis was expressed: the established forms of costing and cost account sufficient enough to provide proper identification and calculation of the real cost of information acquired from third-party sources, i.e. from actors operating under the changed context of information society and knowledge-based economy. The above statement was unequivocally falsified. The forms of expenditure associated with the acquisition of information from third-party sources represent a clear departure from the traditional understanding of costs. In effect, the established approach to costs and cost calculation cannot possibly be regarded as sufficient for the identification and estimation of costs incurred in the acquisition of thirdparty sourced information. This critical evaluation of the traditional forms of cost accounting should not be interpreted as voiding them of their undeniably practical values. It should only be taken as a simple statement of their limited utility for the practical demands of identification and estimation of costs of such acquisition. By reducing the scope of such analyses to the limits of traditional cost accounting models, we may lose track of a lot of important real cost items which have their bearing on decision-making processes or on the balance represented in cost-to-benefit analyses of specific endeavours. The second research hypothesis was expressed as follows: it is possible to extend the traditional cost accounting models to include the representation of other costing categories. The statement was successfully verified in the course of this research. It may safely be assumed that there are no cognitive or methodological barriers to bar a successful inclusion of new costing categories. Problems with the new categories are not in their coherency with other items, be it new or already established. They are more likely to emerge in relation to such challenges and barriers as: •• the difficulty in clear and unambiguous identification of certain costs and their practical manifestations, •• limitations and deficiencies of the economic dimensional analyses of expenditures (costs), both those expressed in natural and monetary units, •• difficulties in establishing a fair market price for such items to serve as basis for detailed calculations, •• the largely subjective character of most evaluations based on unconventional methods and approaches to the valuation of this type of costs. The above problems were properly exposed in this research, together with suggestions for further scientific exploration. The author also emphasised the need for an individualised approach to the identification and estimation of the new categories of costs (with each activity examined in separation from others). In addition, based on literature studies of modern economic sciences, particularly the welfare economics and the transaction cost economics, the author concluded that the latter two schools provide a good foundation for the postulated expansion of the established cost accounting formulas to allow for the inclusion of the real cost of information acquisition. The transaction cost economics can be employed not only for the identification of this group of costs, but also for the effective estimation of their levels. The neoclassical economy (and the welfare economics), on the other hand, allows for good recognition of the nature and the economic significance of alternative costs. These represent a category of hypothetical costs which require no real expenditure, but serve to expose and emphasise the alternative and scarce character of economic resources. This, in turn, allows for practical inclusion of alternative costs as part of the established cost accounting and decision-making applications. The welfare economics has also contributed to the proper exposition of another important group of costs - namely, the social costs. As evidenced in numerous empirical studies, practical significance of social costs has grown over the years, and for many reasons: not only due to the variety of their forms and manifestations, but also to the systematic increase of their levels and their practical impact upon the effectiveness of economic endeavours - both in micro- and macro-economic dimension. They also represent real costs, and are often required from economic entities other than the real guilty party. This may generate additional difficulties, both theoretical and practical, in relation to the internalisation of such costs, i.e. their proper attribution to parties held directly responsible for such costs. The above elaborations present a precise response to the third research hypothesis under examination, namely: types of cost currently unrepresented in cost accounting models should be included in the examination of the real cost of information acquired from third-party sources, i.e., from actors operating under the changed context of information society and knowledge-based economy. They not only allowed for the proper identification of their forms and types, but also helped emphasise some of the additional aspects to be included in this type of analyses. For instance, the most important challenges in the context of transaction cost are based on the triad of: identification - classification - valorisation. Even if we manage to properly identify the types of costs, we still need to overcome two important problems associated with the use of transaction cost in micro-economic account calculations, namely: the attribution of their levels in natural units, and their monetary valorisation. These pose their own sets of interesting problems and dilemmas, both from the methodological and the practical (accounting) standpoint. For research hypothesis four - the new category of cost, i.e. the real cost of information acquired under the changed context of information society and knowledge-based economy, represent a significant portion of the real cost of such undertakings - the verification was obtained at levels which may raise reasonable doubts. Based on the available empirical data, the author demonstrated the intensities of certain phenomena associated with the acquisition of thirdparty sourced information, both in micro- and macro-economic dimension. This may be seen as a confirmation attesting to the validity of hypothesis four. Perhaps further verification can be found in the detailed analyses of volumes of the associated costs for individual undertakings or - in an aggregated form - for the economy as a whole. Such an endeavour would surely prove expensive and time-consuming, and would be far beyond the capacities of a single researcher. With proper logistic support, however, the task may be seen as a challenge worthy of further exploration. Apart from the examination and verification of theses and research hypotheses, this work has hopefully brought some order in the understanding of several important cognitive notions. This was a necessary step, dictated by the nature of research material, and the apparent lack of transparency in the commonly adopted definitions. Moreover, the author hopes to have achieved a thorough evaluation of the utilities offered by the concepts of the welfare economics, and modern economic sciences in general, for the practical examination of the real cost of information acquired from third-party sources. Another notable benefit of this approach came as a natural consequence, resulting in a clearer identification of the main research dilemmas and challenges in the studied field, as well as some of the practical obstacles in this context. This forms a good basis for further development of knowledge and skills in more precise identification and estimation of cost associated with the acquisition of third-party sourced information. The implicit objective behind this research and behind this monograph was to place due emphasis on the notion that - in face of the modern rise of information society and knowledge-based economy - the problem of the real cost of information acquired from a third party may prove exceptionally important, not only for cognitive, but also for practical (implementation) reasons and standpoints. The cost of acquisition, or - in a broader sense - the cost associated with the realisation of the information function, will quite soon elevate to be a major measure of effectiveness in any decision-making scenarios and planned endeavours related to information management, or for the entire information management system on the level of individual entities. As such, it will also be of major impact upon the broadly defined effectiveness of information society as such, and of knowledge-based economy in its entirety. Lastly, it may bring important improvements to the existing approach to cost accounting on the macro-structural level. These are the tasks for the immediate future, ones that must be faced quite promptly, both in economic research and in management practice.(original abstract)