> Who will buy the phones when no one is paid to produce them? The cars? The food and the clothes?

Other wealthy people. I knew someone in the yacht-building business who would say "If you want a business that will last, sell to rich people--they're the ones who have money." We are very quickly moving towards a world where the economic activity (earning + spending + producing) of the median person is insignificant next to the activity of the very rich. There are individuals who have more wealth than the GDP of entire countries.

We're bifurcating into a society like the movie Elysium: A relatively small number of wealthy people who matter to the economy, and a huge number scraping by day to day whose economic activity amounts to a rounding error in the grand scheme of things.