The cloud computing ecosystem comprises hundreds of providers, offering diverse computing services, incompatible APIs, and significantly different pricing models. Cloud application management platforms hide the heterogeneity of the services and APIs, allowing, to varying degrees, portability between providers. These tools remove technical barriers to switching providers, but they do not provide a mechanism for evaluating the cost effectiveness of switching.This paper presents a decision support system, working within cloud application management platforms, that evaluates the costs of a customer's applications using resources from different cloud service providers. The system (1) generalizes and normalizes multiple cloud pricing models and (2) gathers pricing data from cloud providers. These, in conjunction with the application resource consumption model, allow the cloud pricing module to estimate a price for the application for each cloud provider.To demonstrate this, our cloud pricing module has been integrated with the SlipStream multi-cloud application management platform, allowing its users to optimize their choice of provider(s).