Legally, if they advertised it at a certain price and you tendered payment at that price, they have to sell it to you at that price: they made an offer, you accepted it, and therefore an enforeceable contract or agreement to sell at that price was entered into. Practically, you can't force Amazon to intervene, since was a 3rd-party seller (not under their control)--you'd have to sue the seller for the goods, which may not be cost-effective.