It is nice, but not relly the right way to think about it. The purchasing power of money does NOT equal to market cap of everything divided by total units of currency, but from supply and demand for money, that is demand for holding the units of currency (desire to hodl).

To ilustrate, imagine a world where bitcoin is universal money, and everyone has a desire to have 5% of their net worth in BTC. Now immagine world where it's 25%. Massive difference. It works like all other market prices.

Note that 25% in money is crazy high in a world, where bitcoin has become stable hard money, and is not going to the moon anymore. In Hal's argument the number would be 50%!