Re: Hang on
I'm fairly certain there used to be something in the distance selling regulations that protected online sellers with regards to incorrect prices etc. Looked it up when somebody tried to buy an £89.99 phone which had been priced at £8.99 and they hadn't honoured the reduced price. (Cancelled the order on the store end)
IIRC it was basically along the lines of "Until the item is marked as shipped, they have a right to cancel the item". I imagine Amazon / sellers could use these same rules here, unless the item was automatically marked shipped before the mistake was noticed, at which point they're in a legal hole and would have to eat the costs unless the buyer was especially nice.
Biting the hand that feeds IT
