How much is camping equipment in the U.s.?

I am going on a holiday to the USA and am planning a lot of hikes and camps. I was wondering whether or not I should buy camping gear that I don't have here or over there. How much are two-5man tents, sleeping bags fit for late Autumn/Fall, hiking shoes...What else should I take/buy if I am going to the Grand Canyon, Yellowstone in early september to late october? Your help is very much appreciated, thankyou! :)