The extra content is probably not worth the money solely for the extra content.
But I agree with the second poster. If you're looking to give some extra money for a GREAT game, you should go ahead and chip in the extra ten bucks. I am unemployed and have zero income, but I did. (I also have a machine that is under minimum specs. The game, however, runs if I am on minimum graphical settings. It hasn't unexpectedly crashed yet, though after two hours or so, I have to let my computer cool off.)