Am I Liable for the Difference if the Seller Sold Me Something for the Wrong Price?
Typically, in such cases the adversely affected retailer must show that enforcing the contract would be unconscionable or that the shopper knew or should have known that the price was a mistake. Mistake covers a broad set of situations, and courts often distinguish between unilateral mistake and mutual mistake. A unilateral mistake is an incorrect belief of one party that is not shared by the other party. A mutual mistake is an incorrect belief shared by both parties. Courts have traditionally held that mutual mistakes are more likely than unilateral mistakes to make a contract voidable.
Where only one of the parties is mistaken about facts relating to the contract, the mistake will not prevent formation of a contract unless the nonmistaken party is or should have been aware of the mistake made by the other party, or if the mistake was due to mathematical mistake in addition, summation, subtraction, division, or multiplication and was made inadvertently and without gross negligence.