Seller doesn't want to sell

[dad_of_one_autistic_superhero]

Seller claims he accidentally listed "buy it now" item for the wrong price. I bought all three of the listed item, promptly paid, and was later contacted and informed by the seller that they meant to list them at a higher price. I feel like the seller is attempting to extort more money out of me. A "buy it now" purchase is a legally binding contract correct?