I saw a single new copy of this game for $12.99 at my local TRU a couple weeks ago. My roommate almost had a heart attack, since he'd been looking for it forever...ran out and picked it up the next day Oddly enough, the XBox version was on the shelf for $49.99.
Nothing odd about the Xbox version being full price. The Xbox version is a relatively recently released Director's Cut with many nice extras and shouldn't yet be expected to be as cheap as the older PS2 version.