If you look at the link provided Woges provided, you'll notice that it says 'new and improved' and that the platform now says 'Windows XP/Vista'. That alone could justify the 18£ (18 British Pound) for this new release of a 10 year old game.
I haven't seen any new release of PS: Torment, at least not here in Europe, unless of course you count the games of Forgotten Relams Collection box. I still think this only was the CD-version, though.
Baldur's Gate 1 did get a re-release on DVD several years back, I think, Atari released such a version 2001? or maybe 2002? BG2 did also get a re-release on DVD, at least in Europe.
Atari must have thought there would be a market for PS: Torment, since they have re-released it...