For many organizations it is difficult to determine the total costs caused by offering own services in the cloud as well as to compare them with the costs caused by an in-house datacenter. In practice, some models exist that support organizations in analyzing costs. However, these models are mostly static and do not consider the dynamics of cost development when using cloud computing. The purpose of this paper is to design and develop a simulation model that covers such dynamic aspects and supports decision makers in analyzing cost-benefits of cloud computing versus own datacenter. The model is based on a theoretical framework for IS and applies the method of system dynamics.