So the short story here is:
If your a l33t gamer (iMac buyers are very rarely) have the skills and time to built a system from scratch (still not the typical iMac demography) can live with having a full tower cluttering over your desk (completly different market, but who cares) and are willing to spend a few 100$ more you can buy something better than that iMac.
Well not really, as you also have to wait a few months for the components to become available.
So yeah it's prooven that iMac costs twice as much as it should !!!