I think there’s an interesting and fair argument to make that one negative consequence of billionaires is entire otherwise unproductive economic sectors that exist for no reason other than their vanity (mega yachts, Swiss boarding schools, high fashion, doomsday bunkers). That is a different argument than one about resource hoarding though — a Louis bag doesn’t take much in the way of resources, just a single python in the worst case!

>one negative consequence of billionaires is entire otherwise unproductive economic sectors that exist for no reason other than their vanity

This isn't just relegated to billionaires. Depending on how you define "consumption", up to 70% of the U.S. economy is consumer driven. Now I wouldn't call all this "unproductive" but it's probably selectively unfair to claim only the uber-rich are spending money on items they don't need.