It really depends on the location (country specifically) and model. But for a decent guess, in the USA a working PowerMac G4 (single processor) WITH HDD, RAM, and cable can go for as little as free to up to $55 + shipping on Ebay. Craigslist may sell for a little more to an unsuspecting person, but not much more. A higher end PM G4 can go for more though. They just are not worth a whole lot now. The whole PM series, including the G5 has come down in cost by about 25-35% over the last year here in the USA. At least this is my experience selling them on Ebay and Craigslist.