The price of a Lion upgrade is pretty much immaterial, as the relevant price of OS X is really bundled into the price of the hardware. You cannot buy a Lion DVD and install it on a non-Mac PC.
It is if you care about staying withing legal bounds and thus respecting their EULA.
Also, OS X is not designed to run on any hardware, like Windows or Linux -- basically you have to ensure that you get the same configuration that Macs have, or you're sure to run into trouble.
This means that if you already have a desktop or a laptop, you most definitely won't be able to run OS X on it, at least without pain; instead you're far better off buying new hardware and you're even better off going for an original Mac instead, or just not using OS X altogether.
I mean, yeah, I know some people are happy with their hackintoshes, but it has been a poor experience for me and I just reverted to my reliable Ubuntu / Windows combo.
