Many of these people don't have fortunes from consumer goods. An awful lot of them are making money out of thin air. They create markets that rise, bubbles that grow, manipulate markets, etc., and the value of their investments go way up. No products were created, distributed, purchased. That's too much trouble. Better to just manipulate numbers on a spread sheet, and voilá, wealth out of thin air.

That just works when the people buy directly, not thru government contracts or subsidies.

It's of just Musk, it's billionaires as a whole. One may have very hard time not buying anything from them while still surviving.