Valkyrie Profile for PS1 didn't go down in price even though it was remade for PSP as Valkyrie Profile: Lenneth.
I think the collectors keep the prices up where they are. I haven't checked to see if the original Dragon Ball GT: Final Bout US disc is still worth anything but it still probably counts as a collector's version. EDIT: This one isn't. It's gone from like $150 to $30 online. But that's probably because it didn't really control that great (all choppy and stuff).