I used to work for a high end art gallery in New York. I was told there the market for people who would purchase $100,000+ artworks was 2,000 people.
So depending upon what level of price point for audio gear, I’d guess somewhere in same order of magnitude.
i know a good amount of upper middle class with basic McIntosh systems probably at $25k total.
But that’s just based off the day point I know.