[CannonFodder52]

However I don't know where the line is drawn between clever bartering and sharking here, so I've never been inclined to try it. Especially because I'm not bartering with an incorporated drone but a real person.

Interesting tactics you got there.
But ya its not really sharking unless the other person doesn't have a slight grasp on the price of his item. If they roughly know what its worth and you barter them down, its not sharking.
Although if you are blatantly lying to them about the value of their hat, people usually consider that to be on par with sharking.