I agree. It's really not worth your time to buy a disc-only game unless it's incredibly cheap, like a dollar, or incredibly rare. Trying to get rid of a disc-only game on ebay or elsewhere is near impossible unless part of a bigger lot, especially if its surface isn't flawless. I even avoid ones without the original manual.
I'm finding that a lot of local record stores are getting in a pretty nice selection of xbox titles, since folks turned away from GameStop had to find somewhere else to unload their games. The prices can be iffy and inconsistent, though, but at least they price them differently based on condition.