An increasing number of providers are offering utility computing services which require users to pay only when they use. Most of these providers currently charge users for metered usage based on fixed prices. In this paper, we analyze the pros and cons of charging fixed prices as compared to variable prices. In particular, charging fixed prices do not differentiate pricing based on different user requirements. Hence, we highlight the importance of deploying an autonomic pricing mechanism that self-adjusts pricing parameters to consider both application and service requirements of users. Performance results observed in the actual implementation of an enterprise Cloud show that the autonomic pricing mechanism is able to achieve higher revenue than various other common fixed and variable pricing mechanisms. Key words: Service Pricing, Autonomic Management, Advanced Reservation, Quality of Service (QoS), Utility Computing, Cloud Computing