The worst over pay I ever did on one was when a guy at a Funco-Land store told me his roommate had Sinistron (This was many years ago) and I started badgering him about asking the guy if he'd take this amount or that amount.
Needless to say, I got played for $40.00 and ended up with just the game in a cracked case with a missing stabilizer.
I knew even back then, I'd over payed but, at the time was under the impression that the game was ultra rare.