Are you sure it wasn't just a pricing mistake that the particular store made?
Just to let people know the LE version has the following extras:
[quote name='"GameSpy.com"']Packed inside a special tin box, the Limited Edition features a figurine of lead hero Altair, a set of Penny Arcade comics, a Mini-strategy guide, Assassin-themed short films, and additional Assassin's Creed videos[/quote]
I'm not sure if that would be worth an extra $20...
Thanks for the post though.