Is this a mutual mistake or a unilateral one? If you knew the price to be unrealistic, then you might be unable to enforce your purchase . Find out who made the mistake-was is the person who entered the incorrect amount on the website who didn't work for the seller or the seller themselves? Contact a local lawyer who knows about these types of situations. There is a truth in advertising statute that applies here.
The responses provided to your questions are not legal advice, do not create any attorney client relationship, and are provided for informational purposes only.