I've been tempted to sell my copies of Vagrant Story and Valkyrie Profile in the past, but I never did. Those games are just too awesome.
I think my most expensive single game was Mobile Suit Gundam Battlefield Record 0081. That was like $80-ish plus shipping, but that was standard for a new PS3 game. I tended to shop for deals for all of my old stuff. Now, the most I've ever spent on one gaming thing is either my imported Sakura Wars collection (1-4), Growlanser collection (1-3), or Super Robot Wars Alpha collection (A1, AG, and A2). I just can't recall which was more. I *think* Sakura Wars was more than either of the others, but I got it years ago so I can't be sure.
Either way, all three of them were more than my Langrisser collection.