The catch is that although they are only charging 50% of the regular ticket price for Iron Man 1, they aren't going to sell a double feature package for both films. You have to buy them separately.
That's utterly stupid.
This is why AMC will never be as good as the Alamo Drafthouse. I've written several times about my love affair with the Alamo. Started by a couple of film geeks, it is the absolute best way to watch a movie.
Way to fail, AMC.