The best deals I've found are on auction, so may be an idea to keep an eye out - depending on what condition you're hoping for one should easily be had for that price range. Note that many of the cheaper ones don't always include HDDs (therefore no OS) or RAM modules so remember to factor those costs in.
Also, have you tried websites like Gumtree or Preloved for local listings? some owners are willing to ship at your cost
Don't know you're purposes for the machine, but if it's more of a server or similar purpose machine then a G4 would be more suited (more power efficient, stable, etc) and with PCI expansion, SATA II can be added easily (bette r than G5s SATA 1) -Also with option to install more HDDS and also faster Ethernet networking solutions.
Also, a high end G4 (dual) will be at least as quick as a low G5.
Hope that helps a bit, sometimes you have to wait a bit to secure the best deals..
