Tribulus terrestris is the #1 selling testosterone booster, and the best example of a supplement that increases libido, but has no effect on testosterone.
Ab belts may cause muscle contractions if used properly. But the belt alone cannot produce six-pack abs. The real challenge to ab definition is the layer of fat that lies right under the skin, hiding muscle tone.
The belt was probably about 10$. But that doesen't mean you got ripped off. He's doing you a service, and you paid for it. There's much more to the cost of his service than simply the cost of the part.