> If you accidentally purchased a bag of M&Ms from Amazon for 500 dollars instead of 5, they will let you undo it. On the other hand, if the matter is reversed, Amazon is expected to be a good sport and take the loss

Your "reverse" is not the inverse situation, which is what you should be really comparing against.

The real question you need to ask is what people would do in Amazon's shoes. The answer to that is far less clear to me.