This is just the market cap effect. You can't buy or sell a company for its market cap; usually the real price is much higher or lower. Likewise just because you can buy or sell 1 BTC for $15 does not mean that 6.7M BTC are really worth $103M.
With a market cap there is still a finite number of shares, there aren't new ones being constantly created. We're also talking about a commodity, not shares of a company which is a value creating entity.
