The stock market converts stock into a (more) liquid asset. The value of GOOG may vary day to day, but no one thinks that it's difficult to turn shares into cash.
Turning oodles of shares into cash at the prevailing price, without pushing the price adversely, is quite a trick. "Slippage" is how to research this concept.
Who suddenly needs $3 billion out of the blue? Because Bezos regularly cashes in over a billion each quarter. Is that not enough to maintain a lifestyle?
But if he wants to buy a sports team, he can probably pay directly in AMZN stock as a private transaction (well, except for possible SEC regulations.)
