Best Buy surprises me sometimes, but usually on hardware, they take anywhere from a week to six weeks to get stuff in for sale. Usually they have the floor demo units quickly, but sometimes that has taken as long as a week. They did have the iPad April 3rd, and according to someone that worked there, had a large quantity of the accessories too.
I guess the general word would be it will likely take a week or more for them to get items for sale. And yes, they sell at Apple retail price. Occasionally, they have their 'open box' units but those are rare from the experience of our local store. Oh, and they aren't generally very knowledgeable and will often try to sell people out of the Mac and into a peecee...