In France there is, AFAIK, a law that says that if you buy something when there was a system error setting the price, the company can legally ask you to give th

In France there is, AFAIK, a law that says that if you buy something when there was a system error setting the price, the company can legally ask you to give the item back. Usually they don't because of the PR problem it could cause but a system mistake does not mean that the item is suddenly free for grabs. I do understand people taking advantage of it though, it's a bit like winning a tiny lottery.