The GQ ($200):
Fry's weekly sale. $130 for a full computer (hard drive, cd-drive, motherboard, processor, case, floppy drive, RAM and absolutely nothing else). It comes with Linspire since Windows XP alone costs $130. By itself it can't run WoW since it only comes with 128MB of RAM and on-board cheap-o video. I had a Radeon 9600 Pro laying around I threw in it (amazingly the GQ has an AGP slot) and I bought 512MB of RAM to add to it. In the end I would estimate the computer would cost a little over $200 if you wanted to use it to play WoW as cheaply as possible. You can see the GQ under the desk on the right, the black box back there next to the sub-woofer.
The Black Boxes ($500 each):
I built two identical cases from parts off NewEgg. Initially my plan was to use some old parts I had lying around to build these so I just bought the cases and some hard drives. Turns out, those old parts were laying around for a reason... they don't work. In the end I bought two full computers for about $500 each, leaving out keyboard, mouse, cd-drive, floppy, drive, etc. They actually aren't too bad, Athlon 64 3700 + 1GB RAM + GeForce 7600 GTs. They aren't top of the line but they play WoW fine with all the settings up at native resolution for the monitors (1280x1024). These two computers are the ones stacked on the left.
The Others ($500 each):
The other two computers are computers I had before. Initially I paid probably $1000 each for them but that was a long time ago and I actually think the two black boxes I got are better which is why I listed the price above as $500, because you could get as good/better for that much. They have almost identical hardware and the only thing that makes them any better then the black boxes is that they both have mirrored raid arrays since they are the ones I do most real work on. The black and beige boxes under the desk on the left/right. These are the two computers with CD/DVD drives in them and my primary machines.
My quest to level 5 World of Warcraft characters at the same time.