What are you factoring in for ROI to move to a cloud solution?
Just the cost of removing a room or room of servers to something that is multi-tenet?
Then, you may be missing the true ROI of cloud computing.
As David Linthicum points out (http://www.infoworld.com/d/cloud-computing/what-youre-missing-in-your-cloud-roi-calculations-595), the true value of moving to a cloud solution is the ability to be infinitely more flexible in adapting to future needs.
I take that a step further in the fact that implementing a cloud based solution allows you to not have to overhaul your current IT staff and infrastructure but more easily adapt your new cloud system to what you have. I.e. just because you have an new system doesn't mean you have to scrap or relearn your intellectual capital.