Just because the buyer got an engine for beer doesn’t justify shading dealings.
“You get what you paid for?” - that’s exactly the kind of mentality that promotes scams and rip-offs. In that case, any person can sell a product and not care about repercussions.
Try that in the real business world and see what the results are. Maybe not the first time, or the second time but eventually, one messes with the wrong party and the results are not pretty.