I think video cards have a better life span than we give them credit for. I've got a Radeon 9700 Pro that I probably paid a hefty amount for about three years ago. It's holding up just fine. And my PC has consistently looked better than any of my consoles since I got it. So maybe not five years, but probably four.
That card can be had for like $80 on eBay these days. I just cobbled together a PC which seems to be handling modern games just fine for about $300, tossing some old parts I already had laying around. That's probably kept me from getting a 360 at launch.