Providing effective IT support for business processes has become crucial for enterprises to stay competitive in their market. Business processes must be defined, configured, implemented, enacted, monitored and continuously adapted to changing situations. Process life cycle support and continuous process improvement have therefore become critical success factors in enterprise computing. In response to this need, a variety of process support paradigms, process specification standards, process management tools, and supporting methods have emerged. Summarized under the term Business Process Management (BPM), they have become a successcritical instrument for improving overall business performance. However, introducing BPM approaches in enterprises is associated with significant costs. Though existing economic-driven IT evaluation and software cost estimation approaches have received considerable attention during the last decades, it is difficult to apply them to BPM projects. In particular, they are unable to take into account the dynamic evolution of BPM projects caused by the numerous technological, organizational and project-specific factors influencing them. The latter, in turn, often lead to complex and unexpected cost effects in BPM projects making even rough cost estimations a challenge. What is needed is a comprehensive approach enabling BPM professionals to systematically investigate the costs of BPM projects. This chapter takes a look at both known and often unknown cost factors in BPM projects, shortly discusses existing IT evaluation and software cost estimation approaches with respect to their suitability for BPM projects, and finally introduces the EcoPOST framework. Eco-POST utilizes evaluation models to describe the interplay of technological, organizational, and project-specific BPM cost factors as well as simulation concepts to unfold the dynamic behavior and costs of BPM projects.