Thats a tough question to answer. It all depends on the condition of the bike.
First quad was a 01 formanES... Bought it with 6500km on it. Sold it 10 months later. Only because I hated 4wd all the time, the crappy brakes , no efi, and the Electric shift that would work when it felt like.
Bought an 04Arctic cat 650v2, fast and good get through all sorts of crap, hated the carb, let me down a cuople times in the cold weather, belt blew twice leaving me stranded , overall crap quality. it had 3500 on it.
Bought an 06 Polaris 500x2... 500km on it.. Like new ...mint condition, EFI is amazing, 2up and box come in super handy, never let me down YET. Only bad thing about it is that it wieghts 800lbs ! friggen tank.
In the end its all about the condition.....the price should reflect that