Well luckily we have markets that can quickly turn equity in Amazon into cash. Bezos has in fact been doing that to the tune of billions of dollars a year to fund Blue Origin. I don't see him stopping any time soon.
1) time and time again, particularly in the media, I hear net worth bandied about as though it's the same as cash. Bezos is worth X billion - think what that cash would pay for!
2) billions in equity can't be translated into billions in cash. Millions, for sure. But not billions.
3) any statements that talk about taxing the rich inevitably seem to come down to transferring equity to the state over time based on a current stock market valuation.
All of the above seem misinformed and/or a bad idea, and worth trying to establish fundamental understanding in this area. If you already have that understanding then that's fantastic.