These types of products succeed because of a shared delusion. Take fashion for instance. Everyone believes some clothes are more fashionable than others. The way you dress says a lot about you but why? It's simply because other people think it does. If the delusion runs into reality from the person hawking it, it can collapse quite quickly.
Psychology has a definition named the halo effect and it's very real. A person definitely gains advantages in society when they appear more attractive than less attractive. Naturally people associate good health with attractiveness and it's hard wired in us for finding a healthy mate compared to an unhealthy mate. Good choice of clothing for the frame of a person can enhance personal features and make a person look better than if wearing something less fitting. So there is some benefit & gain that can be made with understanding fashion of clothes as a real benefit. Is the advantage based on a delusion of a person being more healthy than another? Sure, but it isn't because people intentionally have a delusion about one shirt looking better than another.
We are more than hardwired to find the most capable mate. We're also hardwired to pick up social cues so if a large enough group of people believe something, we believe it too. If everyone you knew started wearing those MC Hammer pants tomorrow, how long would you hold out? If people suddenly and entirely stopped wearing ties with suits, would continue to wear the most unnecessary accessory ever? Why does everyone in tech dress so similarly?
If you're a man who wants a wife, this is a clear level headed choice to make. I think delusion as a term should not include optimal choices made by individual actors.
Sometimes it makes rational, logical sense to play the game. It's a form of intentional stupidity. Forgoing your rationality to get the things you want. If you ever worked at a large enough company, I'm sure you understand.
Sure, nobody might expect much of a pair of earrings bought to wear at a party for a couple of pounds, but you'd be upset if you bought an engagement ring and the stone fell out.