I asked that before, and what if all of us sell our bitcoin? But the price of bitcoin is more than the real money how we can get that? Well, I don't think bitcoin has backed up by real money because bitcoin is a digital currency that can change in fiat.
In fact, if we all decide to sell now it is ideally about $131,339,527,800 -----> source
https://coinmarketcap.com/I think there is enough money to do that exchange and more. but when everyone starts selling, the supply will increase, and the demand will decrease, and therefore the price will drop to bring the balance. "down to zero."
if we all decided to sell, no one will trust in the value of bitcoin and so collapse.
When we say "Bitcoin backed by money," it means that it is a guarantee for a certain amount of money. If there is no money, we can not generate more bitcoins.