Who says that the price you paid per share was the actual market value of the shares? For example, let's say that you inherited 10 million options to purchase Microsoft stock at $1/share, and in so exercising the options (by writing a check for, say, $10 million to Microsoft), you then end up with 10 million shares, which on paper, with the current stock price close to $500/share, would be worth close to $5 billion. But could you actually get that much money from selling 10 million shares? Definitely not overnight - so many shares getting dumped on the market at once would materially affect the stock price. The $5 billion number is a hypothetical that depends on other people backing up the hypothetical numbers with their own money (i.e. buying at the hypothetical price) - it is not the same as "I have $5 billion in a bank account and could use that to go buy a yacht and buy political ads etc. with it"