Locally it seems the latest NIB sterns take a value hit of about 20% in the last year or two since our local prices went up a fair amount. If you route a game it will take another hit because it gets a bit more wear and tear, say another 10%. So I would estimate (conservatively) that I would need to take in about 40% of the value of a game when I route it to pay for parts and depreciation.
There is some variability here. A good title will do better than one that fades after the release hype dies down. Buying early in the NIB cycle makes it hard to gauge where a game will sit.
So for me the price of games is important but so is the game itself and what I think its resale value will be. I was all set to by a GB but couldn’t get one early on without a longish wait. That turned into a good thing given the PF issues. Sorted or not it just adds too much risk to a new title still in release hype mode so I dropped out.
By far the best ROI comes from older games. They don’t earn as much but I can buy one, spend a few hundred on parts, and sell it a year later for what I paid for it or often more. NIB are riskier and only really make sense if I want the title. If I was just in it for the money I don’t know if I would ever by NIB.