[BlackyX]

Some might even do it in exchange for something in your server(be it a staff position or something else, depends on the server quite a lot though). Oooor they might also want to receive a cut from the donation the server receives in order to be a developer(if the server has donations, ofcourse). And such similar things, really depends on the developer though, but if he offers absurdly low prices for hard things he's most likely trying to scam pennies or obtain access of your script, so beware.