The problem is that the line where the "obvious" starts is not so obvious. For example, in Mexico there's a law that basically states that a price published is

The problem is that the line where the "obvious" starts is not so obvious. For example, in Mexico there's a law that basically states that a price published is a valid price and as a seller you have to honor that price regardless of how low or absurd it might be. There has been several cases where this has been upheld where you could argue that it was "obvious", e.g., a TV (recent model) sold for like $4 USD. However I believe it is way easier to just establish a "simple" law such as that one, than trying to define what obvious means and what doesn't. I also remember someone explaining me (not sure if this was the real reason or not, but sounds sensible), that it was also to protect from bait and switch scams, where a seller would say such-and-such items sold at X price, really cheap so people would come, and then saying, oh no, it's just an error, it's actually 5X the price. And so the consumer is protected, or at least that's the idea.