It’s like a smaller scale replay of Elon trying to back of his agreement to purchase Twitter last year.

A half-billion-dollar contract is almost certainly going to have re-negotiation procedures specified within (Amazon would naturally be worried that Twitter could easily over-use the services, so they’d want provisions to change the contract in the direction of higher costs - which Twitter would obviously only agree to if the provisions were symmetric). Most likely these provisions exist but aren’t all that binding when it comes to forcing the parties to come to the table and Amazon is dragging their feet on entering the re-negotiation clauses so they can have more months or years of the free money contract.