cavet emptor
If someone wants to put a price on something and try to sell it, that is their business. Is someone else wants to buy something without checking what the going rate is, that is their business.
I don't see any reason to interfere either way.
If you have a question about a product that someone is selling, e-mail or pm them.
Having said that, if someone breaks the rules, we don't need to "let the dogs out" to chew them to shreds either unless they are persistent in their faux pas.