I found this craigslist listing for $50. They call it "High End Late 90s Desktop Computer Setup". Specs:

Dell Dimension l667r - $50
Windows XP
Intel Pentium 3 667mhz Processor
ATI Radeon 9250 Graphics 1
ATI Radeon 9250 Graphics 2
Intel GMA 82810e Extreme Graphics 3
Creative PCI Sound
384mb SDRAM
40gb IDE Hard Drive
CD/RW Disc Drive
Ethernet
2 USB Ports
2 DVI Ports
3 VGA Ports
2 SVideo Ports
1 Joystick Gameport
VGA CRT Monitor
Powered Speakers
Dell Keyboard
Logitech Mouse
2 Power Cords
 

honestly I'd probably have a hard time paying even $10 for that, and all I want is the case.