The reality is that not all workloads are a right fit for the cloud. If you are running highly sustained workloads, then the cloud probably isn’t the right solution for your environment. The systems which work best in the cloud are the ones which can be converted to use the various PaaS services not just the IaaS services. The PaaS services will usually provide a more cost effective hosting solution, especially for workloads which vary over time; for example, ramping up during the day and becoming almost idle overnight.
Even if running in a PaaS environment isn’t an option this may be cost effective for running in an IaaS environment. It all depends on how bursty the workload is that you plan on moving to the cloud.
There are some good points here; check it out.