To be fair, the 1% isn't off either. The figure available was "billions". For ease of calculation, say it was 7b. That means if each developer pays $100 and to

To be fair, the 1% isn't off either. The figure available was "billions". For ease of calculation, say it was 7b. That means if each developer pays $100 and total revenue was 7b, 1% of the world must be a developer. (1% of 7b * $100 = $7b) Also, by your own figure, 20 million is already ~0.25% of the world population.