I want to say $50. I spent I think $29.99 on my dual 1.25Ghz MDD G4 (although it had no ram or HDD and was "As-is") from GoodBytes (Goodwill computer recycling center. it's awesome)

It was listed As-Is and says "Turns on, doesn't boot" They had a tie-wrap on the door handle, but when I asked if I could take a look inside, the clerk was helpful, I cut the cable and looked in. No RAM, no HDD. so I took it home

they had a (LOL) WIndows 2000 Pro disc in the CD-ROM. Not to be sarcastic, but how many techs these days (even the ones that work on their neighbor's machines) actually think putting a windows CD in a mac will make it boot? (short of modern macs, and it involves bootcamp, not just holding down the "C" key

There are better deals out there. Keep looking, but I wouldn't go higher than $50 for a 700/800 and no more than $75 for a 1.42Ghz. It's just not worth it with the outdated tech. I can get a dual 1.8Ghz G5 w/ 4GB RAM locally (on craigslist) for $150 (Not sure if it's still there) with dual 320GB SATA drives.

I would pick it up, but I am completely packed up with machines. No more room, but I think I can live with my MDD (oh and the lombard i scored recently)