What sort of broken? what sort of parts?
electrical broken or physically broken?
Mine looks perfect but the power is screwed, full charge only lasts 15 mins so that is kind of broken but as it will only be the cost of a spare chip and the soldering to get it as new I wouldn't sell it cheap.
Are you after the case ? are you trying to fix your own broken GP2X or working on a mod?
Give us a few details to work with, and look out on ebay
Good luck