I bought a pre-made one for about £750 in 2007 from Cyberpower in the UK. I need a PC for development work but I also wanted to be able to play games, so I spent an extra £150 over what I would have paid on an 8800GT graphics card.
Since then, the only upgrades I've made are £40 for an extra 2gigs of RAM, about the same for a copy of Windows 7, £100 for an extra 1TB hard drive and £25 for a 360 controller- apart from the latter, none of those upgrades were strictly for gaming.
I can still play just about any game at 1680x1050 and medium-high detail, bar Crysis. The tendency towards multi-plaftorm development has meant the 'good' lifespan of my graphics card has been extended, and I expect it to last at least another 18 months.
So, it looks like I'll be getting the best part of 4-5 years of good quality gaming for an extra £150 outlay, plus the cost of a 360 controller. So far, not only have I earned many times the overall cost of the PC through my development work, I've also more than recouped the extra £150 outlay because the games I buy are often £10-15 cheaper than the console equivalents.
For me, PC gaming works out significantly cheaper than (HD) console gaming would have done. Obviously everyone's circumstances are different, but it is true that getting into PC gaming has never been cheaper than it is now and is a great deal for many.
