Microsoft seems to be getting quite curious about a second-hand digital game store. At least a survey that's being passed around seems to indicate their newfound interest.
But the question is an interesting one, and would you sell back your games for 10% of the purchase price? That doesn't seem like much, despite being more than you'd get otherwise. 10% of the usual $60 modern price of a AAA game would net you a whopping $6. You'd be rich.
It's an interesting business to get into, the resale of digital goods that have already been "claimed" so to speak. There are sometimes limited numbers of keys available to access and download a given game, but that's a limit of any database software and not any practical limit. As a longer-term analogue to a return policy, it could help gamers afford the latest, boosting business in the present, but there are other implications of doing something like that. Is this something they plan on having available after a certain amount of time, where a drop in price of that particular game negates any angst at trade-in price and complaints of not being able to simply trade or sell your digital keys to others? It's a start of doing something new, so one would hope they're at least asking all the right questions.