Found this post about the new vSpehere licence model.
Here a piece of the post.
“Before you upgrade to VMware vSphere 5, run the tool below to learn how much vRAM you are currently using and how much you are entitled to under vSphere 5 licensing.
Because vSphere 5 licensing is based on a per-processor basis with vRam entitlements, you need to make sure all license keys you have purchased are entered into vCenter Server.
The following vRAM entitlements will be given per license type:
|License Type||Essentials||Essentials Plus||Standard||Enterprise||Enterprise Plus|
|vRAM Entitlement per License|
Read the complete post here.