The price of bitcoin is just the most someone's willing to pay for it right now. If it dropped to zero it wouldn't mean any bitcoin or USD disappeared, just th

The price of bitcoin is just the most someone's willing to pay for it right now. If it dropped to zero it wouldn't mean any bitcoin or USD disappeared, just that no one wants to buy it; mathematically everything still adds up. The 300B number comes from market cap. Take the current price of BTC, multiply it by the number of BTC, and call that the value of bitcoin as a whole. But that's just an overly simple guess to the total value, not a mathematical fact. Reality is of course more complicated: Imagine the BTC market as an order book. Maybe there's 10 people with an order to buy for 6k or less, 3 people with an order to buy at 5.7k 5 people with an order to buy at 5.5k or less, etc. Then if someone sells 18 bitcoin they'll get 6k for the first 10, 5.7k for the next 3, and 5.5k for the rest; while causing the price to lower from 6k to 5.5k. Since there's way more BTC than this hypothetical person sold, it causes the market cap to lower much more than the amount of money they made. And of course this too isn't static in the real world. Some people may sell when they see the price going down, some people may _buy_ when they see the price going down, and general unregulated chaos.