Learn about contract law, it's interesting. In Germany, for example, displayed prices are merely an invitation to make an offer (”I want to buy this!”) which v

Learn about contract law, it's interesting. In Germany, for example, displayed prices are merely an invitation to make an offer (”I want to buy this!”) which van then be accepted or rejected by the seller. Only if the seller accepts a contract of sale actually comes into existence. By the way, if the seller accepts but changes the conditions (by, say, changing the price) a contract of sale also doesn't exist. The buyer then has another chance to accept or reject this new offer. It's pretty common sense, actually. Oh, and this doesn't mean that sellers can display wrong prices on purpose. That would be misleading advertising. But if it's a mistake it's not a problem.