So the hardened edition is $79.99 USD
The regular edition is $59.99 USD
For $20 USD more, it seems fair to get the 4 zombie maps, and to get the steel case for the game, and a custom outfit for online.
Then if you dont get the hardened, if you want the zombie maps, you'll have to buy a $20 PSN card just to get the maps, and you'll be missing out on the steel case.
It sounds like a fair deal, no?