You also have to factor in that life expectancy of these machines. Usually processors last about 5 years and by the time that happens you're probably going to want to get the latest which will most likely be a different socket and require a new motherboard.

Furthermore, PC enthusiasts and gamers will never be satisfied. These folk live for the next hardware releases to get even the tiniest gain on their overclocks or go from 2x AA to 4x AA. The PC enthusiast community is a force to be reckoned with. Don't believe me? Just check out the plethora of forums out there and see how active they are. I don't see that going away anytime soon.