That method works fine for a product that works as it should but if you know for a fact that something is wrong with it you should disclose that information, not doing so makes you a scammer plain and simple.

I'm not asking that you not sell the lens for more than what I sold it for, I'm completely happy with the amount I got and bought a replacement lens that same night. I'm just asking that you do the right thing and let people know exactly what they're buying.