The most I remember spending on a game was $147 for SS Battle Garegga. I was heavily into impulse game-buying then (about 2 years ago) and bought up anything with good word of mouth behind it.
Was it worth it? No. Not only because of the gameplay, but the case I got was beat up and the manual was water-worn and torn at one edge.
MD Battle Mania II is running in the $150 range, but I've decided to wait on that game indefinitely. At that price, I don't care if I never own it, though I'll always be checking for something closer to $80.
