Can you pay a capital gain tax if you didn't originally invest capital? I mean Satoshi literally invented bitcoins so you couldn't say that he invested X and calculate a gain from X. If X is 0, you get "undefined".
Yes, your cost basis would be 0 so 100% of your gains would be taxed at the appropriate rate.
I don't know nothing about tax laws but allow me to ask you to confirm this: if I dig a piece of capital out of my mind and then sell it I have to pay capital gains taxes on the earnings?
In any case, the poster above who pointed out that Satoshi hasn't liquidated his bitcoin seems to have a good point.