I got to hold cap's shield and thor's hammer while I was there today. I even got to pose with them a little. The hammer is actually quite heavy, but the shield is very light. However, I talked to some of the guys who were displaying them and they said the hammer might way less than the one I was holding when they actually start selling them, because the one there was just a prototype. The reason for that is to reduce shipping costs. Also, they said the following items would probably cost about these prices:
Captain America Shield: 350-399
Captain America helmet: 350-399
Iron Man helmet: 599-699
Thor helmet: 599-699
Thor hammer: I can't remember exactly, but it was either the same price as cap's shield or thor's helmet.
By the way, they also told me that they will probably sell a hammer that lights up (not in a cheesy way) but like those FX starwars collectable lightsabers. The way they described it sounded cool.