Technological knowledge can be understood as a collective good only when its production requires the absorption and integration of external knowledge. Such external knowledge is the outcome of R&D investments that cannot be fully appropriated by firms and generate spillovers. The exploitation of such knowledge spillovers requires specific investments in knowledge communication and absorption, which brings about specific costs. These costs are affected by the structural and dynamic characteristics of technological systems in terms of the knowledge base, the variety of actors and the communication infrastructures and processes. This paper analyzes the costs of collective knowledge production and their implications for the way in which the firm chooses the mix of internal and external knowledge. This choice in turn shapes the evolution of technological systems.