It’s kind of interesting- the asymmetry of moral expectations and entitlement. 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 — even if the purchase was made in bad faith (ie- knowing Amazon mis-priced it but purchasing it anyways.) I’m not going to en…
It's just good PR for Amazon to undo it
Also, as pointed out by other commenters the asymmetry might also be related to the asymmetry in financial resources between the parties involved.
A lot of shops will not honour deals like this, maybe even Amazon in the past (I could well be remembering this wrongly and not be Amazon but other online retailers)