Ignoring the whole "I spent three days over-enchanting a sword in order to maybe sell it as a decoration", this is an instance where the MC being a big ol' dumb-dumb is sympathetic and believable. He's a naive, trusting doofus, of course someone's going to scam him. He doesn't understand the first thing about business, so it's realistic to think more people equates to more sales. It really drives home how his previous sales successes in the capitol were a fluke.
The real issues is to see if the MC will learn from his mistake and get some business sense. And hopefully some common sense while he's at it.