When I shop. I just remember the game when new was $50 or less. So if it is a loose game, no manual or case then I figure if it's one I want no more than $25.
If it's a complete game with no box then I will go up to $50 if I really want it.
If it' CIB I honestly don't care for cardboard so I will go with a cheaper complete without box first.
If it's CIB and sealed well, I just move on as that's just a collection piece.
I want to play my games and I want to play them without going broke. I enjoy the old games still but I am just one of those people not willing to shell out a house payment for a game. Unless it's several games all at once.