Thats a fiction.but if they wanted to they could cash-in and take a lump of gold.
Take for example leverage. You are a saver, you deposit £1000 in a bank, you imagine the bank may use that £1000 to lend to someone and they make (say) 5% interest, and they give you 3% back, they keep 2%. Not how it works. They take your £1000 and lend it to more than one person at he same time, in theory there is no limit to how many times they can lend the same money, but in practice governments apply rules to limit this leverage ratio (the number of people the £1000 is leant to at the same time). So lets say they lend it to 4 people, each pay it back, so the bank makes 20% in total, pays you your 3% and keeps 17%. Isnt money fun. Now you may ask how did the £1000 turn into £4000, its just did, because they said it did, the number were written down and the money came into existences as if by magic.
Money is not energy, it can be created at will if you have the books that keep the total.
The people who are bitcoin millionaires like any other commodity are the people who got in early, those who took risks and got lucky.
http://gazettereview.com/2017/05/top-10 ... llionaire/