If you buy OS X, there is nothing illegal about putting it on a PC if you can manage it. It may be against an EULA clause, but that's not a contractand more importantly it isn't legally binding...at least not in this country (USA).
They can "not support" such use. That's well within their power. They can make it difficult to install on non-apple hardware, and they have done that. But it isn't illegal and there will never be a court case where Apple is suing a user for buying a copy of OS X off the shelf and installing it on non-Apple branded hardware. Because they know they would lose such a case before it ever even made it to a full trial.
And if we can talk about "unsupported" iphone stuff on this forum, then we can talk about running OS X on a PC. And yes, you can do it. The hard part is the EFI-emulation. It's been mostly solved, but of course Apple can break any 3rd party solutions with an "update" to OS X. (Sound familiar?)
If you know what you're doing, you can make a very nice machine and run OS X on it with minimal consequences. It will take a while to get it working, though, and you need some experience dealing with drivers and hardware, but it works. Since OS X arrived on intel processors, it has gotten a lot easier and better. I have seen a couple "generic" macs that are a good bit faster than your average mac pro and cost less.