The basic answer is if you make a mistake, you don't have to go through with the sale (or a purchase for that matter).
That's the bottom line.
As others have said, write and explain and cancel the sale or refund any money paid.
Some have used the word morality. I think it is interesting as my early training in morality stated that someone only had to shoulder the guilt for wrong doing if they had full knowledge, full intention, full consent in the wrong doing.
In this case, the seller didn't have full knowledge or any intention to sell for those prices. So they aren't morally wrong.
They've been careless, ill prepared perhaps.
The buyer will be disappointed.
But there's no reason why a savvy buyer should automatically have the right to insist on sale by a naive seller. and who knows, the buyer may be understanding.
