When I built the main part before adding on it was around $1700CDN. I was lucky and got a Q6700 when it was brand new for $250 instead of $1300 ( <3 Intel connections)
Since then I have upgraded.. 8GB RAM, 2 more 750GB HDD, 1x 30GB SDD for Windows, added sound card to get off the mother boards, replaced two monitors, mouse pad, keyboard.. easily another $1100
And of course to top it all off if I want to upgrade I get hit hard.. need new mobo, ram, proc... but of course I keep the old one together and use it at the same time.. so then it is once again a whole system