21 million was an informed supposition .
As per an email shared by Hearn, Nakamoto proposed Bitcoin's unit costs to in the end line up with conventional fiat monetary forms.

In the event that Bitcoin stays a little specialty, it'll be worth less per unit than existing monetary forms. In the event that you envision it being utilized for some portion of world trade, at that point there's just going to be 21 million coins for the entire world, so it would be worth a lot more for every unit.