They are taking advantage of demand! Over on POTN I have a topic in market watch posting any links I can find in stock. I think two or three changed from the time I posted it in stock to when they went out of stock, and price went up sometimes $50 or more.
I am thankful Allen's Camera did the opposite and actually sold it cheaper. I got it for $339 to my door.
I wonder when the big retailers will get them... I thought they would have arrived by now, since the smaller shops got them a few days ago. With the 5D3, Adorama and a few other shops had them pretty quickly after the smaller stores. But nothing yet I see!