The best way to get a deal like that would probably be to watch a government auction. Schools near me are clearing out of G4 iBooks, powermacs, imacs, and minis by the boatload... I think the lot of minis went for around $15 each. That's probably where this guy got his.
something like these are what you should look for: https://www.govdeals.com/index.cfm?fa=Main.Item&itemid=15&acctid=6543
https://www.govdeals.com/index.cfm?fa=Main.Item&itemid=1&acctid=7060
https://www.govdeals.com/index.cfm?fa=Main.Item&itemid=788&acctid=4788