The satisfaction you get just seems very price-inefficient and lot of that price seems to be traceable to one-upsmanship. What is the special value of the diamonds in the necklace?
For expensive objects, a lot of the price goes into the limited production runs. A number of these very expensive watches ($100,000k+) might be a single unique piece or limited runs of 100. They take a lot of time to develop, the production expenses are high because of the small numbers being produced, and it's reflected in the final price. For higher end mass produced watches, the expense is in the tighter tolerances, materials, and craftsmanship. You can search for macro videos online to see the difference between a typical $500, $5,000, and $50,000 watch. The extra details and care given to the construction of the watches is impressive. Yes, some brands charge a premium for their name. I'm aware of that, however, it doesn't necessarily indicate the buyer is trying to impress others. Someone could buy a Rolex because it's one of the most iconic watches in history and in their mind it's the peak of their watch hobby.
And you see this with nearly every hobby. If you look at the audiophile community, you'll see people with $20,000 speakers in their living room, yet they live a rather modest lifestyle. You can find people spending thousands of dollars on samurai swords to hang on their bedroom wall. These people are not trying to impress the world. They have a hobby and they are able to appreciate these items.
The special value of the diamonds? People have worn diamonds for ages. It's been ingrained in our culture that diamonds are significant as they've been worn by royalty and noble figures over the years and marketed as a symbol of love. They're also the hardest naturally occurring substance on the planet and look quite nice to the eye. Did you ever see a child dress up like a princess? They didn't do it because they wanted to impress others, they did it because it made them feel special. Wearing diamonds can have that same impact. It can make someone feel special, or represent to themselves their own successes and accomplishments in life. I looked at wedding bands the other year. Many of them had diamonds hidden on the inside of the band. If the purpose of diamond jewelry was only to impress others, why would they be hidden on these rings and only known to the wearer?
I'm not going to say expensive objects or diamonds are never used to impress others. I'm only saying that's one of many reasons why someone might make such a purchase. I don't think it's appropriate to see something of value and automatically assume the owner only bought it to impress you. If you talk to them about the purchase, they might be able to talk your ear off about their passion and what that object means to them.