My wife's book was on the NYT and Sunday Times Best Seller lists and for a while the book was doing phenomenal on Amazon. I don't recall if Amazon ever had it listed as a best seller or not.
Even if you say that a best seller list is manipulated, it's still books being sold even if someone bought it to pump it up. Plus, when it's on the best seller list, the list gets the book title in front of more eyeballs, allowing for even more sales.