It seems like every game these days gets a limited-edition version at launch. Sometimes the extra goodies are nothing more than a download code, but no matter how big or small the set is, getting one means paying $10-50 more than the standard MSRP.
Internet comedian Stuart Ashen takes a number of silly to down-right pointless "special" versions of games to task in this video:
I'm actually a sucker for things like this. If a game I'm even mildly interested in has a limited edition, I'm likely going to buy it. That's why I have mountains of collectible figures, messenger bags, and necklaces I'm never going to use.