Anything that gets to collectors status always shoots up like that, it's silly to be honest but if it's a hard to find game or in limited supply they get away with that.
I was after a 2nd copy of Castlevania Syphony of the Night to replace my broken copy when I joined the forums and I gave up on the idea because they where going for silly prices even with the OST and manual missing, I ended up getting a downloaded copy instead and burned it
Sounds like you may be better off looking at the prices of a 2nd hand PS2 rather than the game
P.S. edited my post in your thread
Added those few you got to play, I hope you can get back to playing them though I know it sucks when a console kills itself just had to replace my Dreamcast, as it happens I just got that today.