This is a good question but it can be hard to tell externally the reasons for people to do what they do.
Currently we don't own a car and use zipcar when needed. A few months ago we had some family visiting and we needed a car for a day trip. Usually I just get the cheapest option, but since we were going to be in the car all day and we had guests I grabbed an Audi G5 (only like a $20 difference for the whole day). That car was awesome. I loved everything about it, how it rode, how it drove, the layout of all the controls. Even the dog liked that car more than the ones we usually get. I have a lot of financial goals to meet before I could justify buying a car that expensive (if ever), and when we inevitably have to buy another car I'm hoping to keep the cost under $6k, but I could definitely see myself doing it. If I did though, it would have nothing to do with external validation, but from someone else's perspective there would be no way to tell that.
Consumption level vs what they can afford could be an indicator, but not always. Some people just buy what they want regardless of if they should. Doesn't necessarily have to do with others.
The whole picture could give you an idea as well. If I bought an expensive car, but lived in a modest house, rarely ate out, gardened, still used my bike as primary transportation, all other things mustachian, etc, it would be easier to surmise that I just like having a nice car and am not trying to impress others.