Yeah, I'm still not buying it (see what i did there
). To the what are you looking for, nothing bit: that's because saying "i don't want a shadow following me around vomiting bullshit so frig off and die" is socially unacceptable. The buyer is often looking at the situation that the salesman is a flat out lier, so what he does to hold onto his money is fine. The fact that a lying greedy salesman is a stock character and a cliche kinda says it all. Same with the guy selling stuff on the street/market/door to door/stock broker, all stock characters that are notoriously shady because they sell stuff for a living. Like the banker profession, it's a profession that has been held at arms length by most people and viewed as unholy and corrupt. Trying to flip the script and say the customer is the bad guy is ludicrous, but you're right, they will likely lie according to how they view you.
If they don't trust you, they will lie again and again because they assume you are too, so if they are lying to you it's a moment to reassess why they think that way before moving forward. If they do the "it died yesterday" shit, it's best to stop, call it out, and then reassure them that you are there to help them deal with this problem safely and for a fair price. Uncomfortable honesty is the only way forward, but for many people/ businesses that's not acceptable. Rather than trying to stick people with crappy merchandise the proper thing to do is take the loss, but that isn't how it works is it? So honestly, the reputation is often deserved.