This is actually a case study for undergrads, Online price changes after the purchase has gone through was once the hot topic. Unfortunately they are within their rights as the listing price is not legally binding. It’s an invitation to treat and the offer is never unilateral, or has it been accepted until they issue the dispatch confirmation email.
There is a valid counter argument that the order confirmation would communicate acceptance, but as your charge will be pending there is no consideration. There is also a term (escapes me) that essentially rules the order confirmation as “if accepted your order will be this, cost this, and arrive by then”. However Amazon have been known to honour prices as goodwill, another poster suggested they offer a gift card for instance. It comes down to contract rather than the consumer debate.
Qualified lawyers can use bigger words, but this practise is at worst dishonest rather than illegal. Sorry