Likle anything, people have realised its now become a 'must have' game for obvious reasons so have ramped the price up to match that demand, you need it so will (reluctantly) pay what they are asking
I paid £20 for Zelda 2nd hand from Game when first starting softmodding and wasn't very happy at paying that for a 2nd user game but had no choice as I couldn't get a copy anywhere, not even ebay offered better prices and once O took into account postage and aggrevation in trying to actually win teh auction I gave up and bought it locally