I’ve been thinking about this question for years without really understanding it.
Let’s say Bob invested a small amount of $100 in 2013, and now it’s worth about $90,000, which is a pretty significant increase. For example, he can comfortably trade on Coinbase to get cash from a real bank.
However, if Bob had invested $1,000,000 in Bitcoin in 2013, he would now theoretically have around $900,000,000. But when he tries to sell those coins for real money, he thinks it might be pretty difficult to find someone willing to pay $900 million to buy his coins. Also I’m sure Coinbase and other trading platforms won’t allow him to sell that many coins.
In this sense, he doesn’t actually have $900 million and he’s not that rich. So now the question becomes how much money he actually has in the sense that he can sell the coins he has and get immediate cash.