Effective information systems have become key to sustainable business practices. However rising costs of operation and a growing system complexity are driving the search for a more efficient delivery of corporate computing. New technologies in the emerging service world such as cloud computing provide powerful alternatives to traditional IT operation concepts. Nonetheless, executive decision makers still have reservations about migrating to this new technology. In addition to security concerns, a key issue is the still prevailing lack of strict SLAs in these service offerings. In fact, service providers hesitate to offer strictly binding SLAs because assessing economic risk exposure is a major challenge. In this paper, we present a novel model for sustainable SLA design for enterprise information systems. Our model combines various state-of-the-art concepts from the field of system management and balances the failure risk with the cost of operation. More concretely, our model helps IT decision makers to understand the relationship between the operation cost and the service quality. Consequently, the minimum economic price of a service and the corresponding operation strategy, given the customer requirements and the infrastructure characteristics, can be determined based on our approach.