At my former employer we had a whole aircraft financing unit, a wine banking unit, as well as an art banking unit - the solutions and services where amazing and for this particular problem the easiest way for a billionaire was to pledge his own company shares with a bank and get a loan, usually $50m could get paid-off simply from dividends over 1-2 years again. If you are in this bracket of wealth, you‘ll have access to highly creative solutions again. However, as you mentioned, sometimes the pressure and challenges are bigger - billionaire’s wealth fluctuates much more than average Joe‘s.