when regarding to the newly released vSphere 5.1 and pricing. Vmware has just announced the death of vRAM pricing (and now you can have unlimited vRAM at no extra cost) , and here are the new prices for vSphere 5.1
Remember the prices here are at PER CPU basis. So for instance if you wish to have a server with 2 x CPU you need 2x Licenses.
Here are the different versions and the feature sets –> https://www.vmware.com/products/datacenter-virtualization/vsphere/compare-editions.html