I mean as far as I know no human being is even a billionaire anyway if you only count cash. It's one of the things the "eat the rich" crowd is particularly bad at internalizing, that there's a difference between value and money that can be spent on food or hospitals.
It is much more feasible for Jeff Bezos to sell a billion dollars worth of Amazon tomorrow or Bill Gates to sell a billion dollars worth of MSFT tomorrow than it is for Elon to sell a trillion dollars of SPCX even over a year's time
I get that net worth is more than just cash, and that is not what I meant and it's pretty obvious that isn't what I meant. It may not just be cash on hand but if an asset is completely illiquid at it's purported value, is it actually worth that?
2,000 gold bars were stopped out of iraq. and that is just what was stopped / reported.
Dictators and autocrats may or nay not have cash sitting in a bank account, but there are most likely multiple with $1B in gold.
Somewhat doubtful. (The first part of your statement, anyway. Of course the difference between abstract "value" and hard, spendable "money" is a thing.)
Like Mr. Hanson said in my sibling comment, some rulers are (or were!) bound to have amassed incredible amounts of resources. For historical/non-present-day examples, consider looking into figures like Jakob Fugger or Mansa Musa.