Rare as hens teeth here, even really bad banged up PAL examples fetch astronomical ammounts of "£'s". It may be genesis but it isn't worth that much if you ask me as it is so limited to upgrades.
Its funny, I say that about the A500 here. Any "real" upgrade other than the 501 ram expansion is so outrageously priced, it make you wonder why the thing is so popular. I ordered a few PAL A600 from the UK, dropped a 3.1 ROM and a CF card inside. I use the North American power supply and the unit has more use than any A500's I have.
I really am confused when people say the A500 has so many "upgrades" because, obviously they are just not available at all in North America for a decent price.
Infact, the A1000 is so much easier to find upgrades for than the A500. (in Canada anyway).