A large portion of billionaire wealth isn't reinvested in productive assets. It comes from holding onto assets like corporate shares and land that grows in value based on the asset's ability to extract profit or rent. Or from distorted (speculative) demand for that asset that is completely detached from its productive output.

Someone like Bernard Arnault is worth around $160B (wealth from luxury brands like Louis Vuitton, Dior, and Tiffany). That paper valuation exceeds the total national wealth of many entire countries: https://en.wikipedia.org/wiki/List_of_countries_by_total_pri...