The interesting thing is not even that high fashion is largely meant to signal wealth. People could be wearing some random tracksuit and show of their wealth with jewelry - that is actually a saner investment resales value wise. But that would be called "ghetto", "not classy", largely because it is so obvious.

High fashion is for people who want to show off wealth while not looking like someone who wants to show off wealth. Counter-signalling - people trying to look like someone who does not need to look wealthy anymore, because the people who do are middle class and these people are one level higher.

But since even this is too obvious, about 10-15 years ago a new category of people (I think it overlaps a lot with the category called "hipsters") emerged who purposefully try to look poor / not conventionally rich and yet you can guess they have money because they always have the latest iProducts.