That's a subject of much discussion, and I don't have a good answer. From my implementation and what I have read about others, I wouldn't expect to be saving any money, but that's not really the point. The big pro of VDI is centralized management, and it's definitely saved me some headaches on that front, but as with any alternative solution there's a degree to which you will be simply "trading problems".
Here's an article that may speak a little as to what you are wanting to know.
