I noticed that also yesterday. While I was on the site a text box popped up so I asked about the extended batteries the response was that they were backordered. I checked at the local store and they have them at the 50 percent off deal.
only reason i could think of removing them from the website is a... either they won't be carrying them any longer online, or b, they are actually backordered and won't be expecting them for a while...