I bought mine from Best Buy Mobile... $560.00 but you have to ask them to match AT&T's price. I also bought a screen protector with tax out the door was a little over $600. I like to buy from there because of the insurance plan they offer, you can't beat it.
Just bought a One X off of eBay for $430. I'm selling a 2007 Mac Mini for $300 plus I'll sell my Skyrocket after I get my One X, so it will come out even. I'm very excited to be part of the One X community!