Hmm, for the PC you could try Baldur's Gate. It's a few years old, so chances are good that you can find it for $20 USD or less. It's a pretty good interpretation of D&D (as far as I know).
Star Ocean 2 is a pretty good RPG. It's for the PSX, but still. I think I got it for $15 at a Newbury Comic last year.
Try these lists. Although the reviews probably aren't helpful, it'll give you an idea of what's out there.
PC RPGs
PS2 RPGs