Please take some time to understand what market capitalization represents. There has been nothing like a billion in fiat invested in bitcoin to date. A billion Zimbabwe dollars perhaps, but that's another discussion. The average cost of entry (per dollar) for bitcoin investors is nothing like the current spot price. To assume that you have to believe that all the original holders have cashed out in the last month; the blockchain says it just ain't so. Even that ignores the many miners that got in basically for free.