In fact on the las picture showing Unreal 3 on Iphone posted above, we can see a good amount of polygons, only towers use a lot already.
When you see games on Iphone, there are less polygons use than that scene. I think it have big optimisations indeed, theyv'e done a great job for Iphone.

I don't know when will Unreal Kits for Iphone will be delivered
and what will be the price, i think it will be lot more than Unity.

Let's wait for dev kits and a game.