Actually, very large blocks of stock are often worth more than a simple (number of shares) * (most recent trading price per share) formula suggests because of the control premium [FN1].
As further proof, corporate-level transactions like mergers and acquisitions typically see prices exceed recent public trading prices.
It's true that selling a large block of stock without influencing price can be difficult, but that's actually a relatively 'solved' problem in modern finance - banks regularly enter into complex transactions with clients that need to liquidate large blocks of stock and are worried about the impact on share price.
So in a sense, his wealth is "all on paper" and somewhat abstract. But especially for a company like Amazon, it's certainly not predictably less value than a back-of-the-envelope calculation would suggest.
For large sums, you always run into expense and abstraction problems: real estate is highly iliquid, gold is expensive to transport and store plus subject to market volatility itself, banks sometimes charge fees for exceptionally large cash accounts... sovereign debt and high-quality short-term corporate debt are often used for holding huge sums of cash-like wealth.
Basically, it's risk and abstractions and hand waiving all the way down.
As further proof, corporate-level transactions like mergers and acquisitions typically see prices exceed recent public trading prices.
It's true that selling a large block of stock without influencing price can be difficult, but that's actually a relatively 'solved' problem in modern finance - banks regularly enter into complex transactions with clients that need to liquidate large blocks of stock and are worried about the impact on share price.
So in a sense, his wealth is "all on paper" and somewhat abstract. But especially for a company like Amazon, it's certainly not predictably less value than a back-of-the-envelope calculation would suggest.
For large sums, you always run into expense and abstraction problems: real estate is highly iliquid, gold is expensive to transport and store plus subject to market volatility itself, banks sometimes charge fees for exceptionally large cash accounts... sovereign debt and high-quality short-term corporate debt are often used for holding huge sums of cash-like wealth.
Basically, it's risk and abstractions and hand waiving all the way down.
[FN1] https://en.wikipedia.org/wiki/Control_premium