Prices always varies dependig on the region, support levels etc. When I wrote 250USD is the listprice per concurrent user without support so the price you found for 10 users sounds resaonable.
I mean 4-5 physical server for about 250 concurrent users.
You will most likely not save on capex with a VDI solution, its biggest advantages is lower opex and increased user mobility.
VMware have many solutions in this space, its hard to say which one that will suite your usecase but have a look at Mirage also.
// Linjo