Your view is very considerable, I was also had the same thought a few days ago when I watched a lecture on Shopify where peoplele sell there own products and even do dropshipping. I came to realize that, even if a person who have not money (depends on parent's money) or have no source of income (student), still saving funds to buy new t-shirts, new watches, shoes, spending money on lifestyle, instead of spending the money on themselves as in terms of skills.
Most of the luxury things many people buy nowadays are just for fashion. Although what the OP is talking about is considerable, the thing is that not everyone sees buying luxury things as that many people are buying luxury things just to impress or show up, or they have been known or are celebrities, so they want to be counted among rich people that have the same thing, and that is why many youths keep buying something they don’t mind. Some of them are forgetting to spend money on where more money will come from, which is to just get what they want at the actual time.
Then I thought of the cause, and came up with the advertisement companies, for example a friend "X" is doing some shopping, how these brands use data to manipulate the mind of X so that he do more shopping, they show him cool ads, relevant to his likeness, and onces he saw too many he made up his mind to buy. So in this era, no only rich people are buying luxury brands, poor or mediocre are also buying products (unnecessary).
So overall, money is flowing from top to bottom, but you are right we can also make money by buying the stocked of those products which are being bought by these rich people.
Yeah. Normally many people are out there who we think have the money but some of them uses their last card to purchase cloth. Some people rather be broke and buy luxury thing they don mind to go broke they just want to get the luxury cloth and other stuffs so that they can recognize in where they go or in social media platforms which is kind of bad attitude in my opinion