So the question then is can you disclaim copyright infringement in this way, did Amazon do it right?
They'll probably do the corporate thing and give $50k to a lawyer to check the contract rather than giving compensation for the costs they have forced on their client.
The author and Amazon agreed a contract which they both understood which stated rules (Amazon could vary the price) and consequences (essentially none for Amazon so long as what they did was an honest mistake which it seems this was).
The author had the right to not sign it or to ask for amendments (and not sign if they weren't granted) but whether or not it was a good deal for him or not he did agree to those terms and assigned certain rights to Amazon which they were asserting.
Copyright infringement doesn't involve any agreement between the two parties, it's a simple assertion by one party that they don't wish to be bound by the (legal) rights of the other.
They're not comparable situations and whatever superficial similarities exist it's nonsense to suggest they are.
They'll probably do the corporate thing and give $50k to a lawyer to check the contract rather than giving compensation for the costs they have forced on their client.