The value comes from the same place of gold, and to a slightly lesser extent fiat currency. When something is used as a medium of exchange the item itself gain

The value comes from the same place of gold, and to a slightly lesser extent fiat currency. When something is used as a medium of exchange the item itself gains value from this utility. Bitcoin has no intrinsic value, but it does derive value from how it is used write large. A bet on BTC is a bet its use will increase.