There are consumer protection laws that protect both consumers and sellers when mistakes are made like in this case (at least here in Québec and Canada, it must be similar in the US).
Let's say you're selling a 10$ gift card on your website but through some bug/error it's now worth 1000$ (an easy mistake to make, just forget the decimal place). What if someone bought the 1000$ worth gift card for the original intended price of 10$? I'm sure you would invalidate that purchase and send them an email explaining that it was a mistake, and it would be perfectly within your rights to do so.
It goes both ways too, if a mistake is made that advantages the seller, they have to fix it.
Let's say you're selling a 10$ gift card on your website but through some bug/error it's now worth 1000$ (an easy mistake to make, just forget the decimal place). What if someone bought the 1000$ worth gift card for the original intended price of 10$? I'm sure you would invalidate that purchase and send them an email explaining that it was a mistake, and it would be perfectly within your rights to do so.
It goes both ways too, if a mistake is made that advantages the seller, they have to fix it.