I got the 1M estimate from here. 4.2M == 1M in astronomer math.

> Let’s say we use an assumption for average addresses per person to be 10 — which is just a rough guess — then the ceiling of bitcoin users who have their own addresses is around 4.2 million.

https://bitcoinmagazine.com/markets/an-objective-look-at-bitcoin-adoption 

 Thanks. Sobering numbers. Not sure if happy to be so early, or confounded we’re at these prices 🤷‍♂️ 

 that's absolute scarcity for you :D