Some salesmen only want to "leave no money on the table". In other words, make the mark, figure out what and how much the mark is good for, and get that amount while leaving the mark happy.
I've also seen salesmen talk about selling a product in demand at the going price. Make the customer happy and we cannot know enough to do more.
Over the years with audio emporia, my main complaint wasn't that they were like the salesman making the mark, it was they were so inept they couldn't even or for stupid philosophical reasons wouldn't do that. They actively tried not to take my money. I've run across two who I thought were good. They were honest, didn't try and oversell, but willing to share knowledge when I was young or let me try things out with no obligation. Literally as in not even a quick facial expression of distaste. They were aficionadoes themselves. One was a staunch subjectivist of whom you surely have heard of. The other was more rational. I cannot fault someone who believes what they are selling even if they are wrong.
I have dozens of horror stories where people wouldn't help or refused to sell something they sold, but wouldn't sell it to me or to people I knew. They are bizarre.
Here is one example, I with a couple of friends were traveling to a city for other reasons, but one of them was to check out some amps one of my friends was ready to buy. There was a dealer for them there. So on a Saturday when we had trouble finding parking in an exclusive part of town we found the store devoid of customers. We go in and look around. A salesman literally goes into an office to avoid us. Three guys sit around there peeking out, but offering no help. We asked to talk to one of them, they decided they needed to make a phone call. Surprisingly they had the speakers that my friend also had. So great he can hear the amp with his speakers.
So after 15 minutes of no attention: The amps were one of three in the room with the speakers. Several pair of speaker cables coiled up with none on the speakers. So I said, "what the hell, let's hook these up and hear them". I start connecting the speakers to the amps after connecting the preamp to the amp we were interested in. Only then, does one of the three guys come out (he turns out to be the store owner). Asks what we want and we tell him. My friend had called him 3 days before we were there. He stops me and says we cannot hear those speakers on those amps. We ask why not? His reply: I don't want to sale amps or speakers or preamps. I can provide the most value if you will let me put together a complete system for you. We don't sale systems under $30k and prefer not to sale those under $50k. Hmmmm, would have been nice if he had said that on the phone when my friend called. Oh and this was 30 years ago. My friend asked would he not sale the amps, that he was ready to buy if he liked them. He replied no and walked back in his office. Wonder why his store was empty on a busy Saturday afternoon?
Now this was a little more extreme than some, but some odd variation of that has been my normal experience in shop, after shop, after shop. One of the reasons 85% of my purchases were of used gear. I'm not surprised nearly all such shops have disappeared. Now I'm not homeless, don't dress like it or act like it. It is weird, and I kept thinking this cannot be how they all are. Most were. I've been to "seminars" where they were showing off some of their top gear and explaining it to you. Easy way to hear stuff. Then go back and get again treated as if the object was to avoid selling stuff.