In the case you mentioned I think there are only two uses, educational and for profit. Personal for fun usage doesn't seem like a normal scenario.

As for the Intel model, Sun looked at doing this a while ago. You know when they had big iron at 72 processors. They'd sell a fully populated Server and then you licensed what you needed. When you're not using it, and you're just idling away, you pay the minimum, but when you were on a big project and needed all of the processors you can pay for more. In this case you turned on and off monthly as you needed (if I remember correctly). I think they also managed upgrades to your system and your memory too so it was as automagic as possible. It was kinda like the cloud model but you had the server in your server room not theirs.

In the intel model as long as you pay the same for 3 cores (with or without the potential for upgrade) I think there's a case to be made.