I've mostly only bought older, used, re-import (directly), kinds of games. Fix them up, play or sell. Since I'm a bit anal, I spend a lot on parts... backbox missing a latch? Let's put it on, even if it isn't totally needed. Coin mechs lira? Let's change them.. info cards, flipper buttons, etc. So, a bit more costly then just making them work and leaves the "profit" a bit but I am not ever really planning to buy and sell right away, flipping them (heh), but usually just to keep them and play, all the while making the game better and more profitable once I do want to sell. I probably, usually, come close to breaking even or making a small amount which then just goes to another game. My JJP POTC LE was bought used but still really close to new price, so that's probably the one I'll lose the most on. My WOZ SE was heavily routed and worn, but I got a really good price on it and I'm working on fixing it up to sell since I'm replacing it with a WOZ RR. I have to do the 2.0 light boards, $800, so that's really hurting the bottom line.

That's about where I'd be as well

Do mods really ever truly get factored in to the price? I feel like at maximum it's pennies on the dollar.

Good example. That's one I often see "not included" with the game for sale unless the buyer pays more. The ol "I'm putting the original dmd back in" posting.