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My best recollection about this subject was that it just takes time for both GM and the dealers to get their books updated, but there may also be other things contributing to it.
Contact Jeff and ask him. He seems to be a really nice guy.
I found through his site the 2009 that I bought last week. I sent him a small gift to help support his site. To my knowledge, he is not doing this to make money. But if I were a dealer with much inventory, I would want to support his efforts.
I thought it was extremely helpful to be able to click on the link and see the window sticker for the cars.
Good luck with you search if you are looking to buy.