This seems to come up on every thread like this. Owning 9% of a company that generates ~$80B in profits and employees 1.5m+ people is literally a massive amount of wealth and putting a dollar figure on that is both straightforward and accurate.
Anyone who owns a house can understand that liquidity and net worth are two different things. But shares of Amazon are far more liquid than a typical home.
In case you need a real example, Bezos personally funds Blue Origin by selling around $1B worth of Amazon stock each year. That's 11000 people earning their salaries + a huge amount of capital investment that are all funded from this so-call "imaginary" money. I can assure you that each time those people get a paycheck, it's just as real as yours.