Back in 2007, I had a Dual 1GHz Quicksilver that I bought as-is untested on eBay from a company. I paid 150 or so for it, IIRC.
I got it, hoping and praying I didn't end up with a dead machine. I figured if I did, I could probably recoup my costs by parting it out.
I got it about a week later, inside of a giant 22" CRT monitor box filled with packing peanuts. I pulled it out and it was in extremely decent shape, with no hardware or parts missing aside from a hard disk drive.
I installed a 160GB hard disk, 1GB of RAM alongside the 512MB, a USB 2.0 PCI card, and plugged it in. It booted perfectly. The previous owner even had installed a Radeon 9000 Pro card from a MDD G4 model.
Apparently the person who sold it didn't know how to plug in a Mac.
I sold it in March 2009, to help fund my Intel Corei7 PC build. I got about 500 dollars from it, locally, with a 19" CRT monitor, keyboard, mouse, and Leopard disc.
I miss it though, it was such a beautiful machine. G4s are way too slow for what I'd want to do with it, but one day I may pick me up a 733MHz model or an empty case or two, gut it out, modify a MicroATX PC inside of it without mutilating the case horribly, then turn it into a Hackintosh.