This reflects a misunderstanding of the drivers of mining costs.

Mining only costs a lot because coin value is high and the block reward is high. This means miners are willing to spend more to win the reward.

As the block reward lowers then mining becomes funded entirely by equilibrium-priced fees.

Oh I understand mining economics quite well. The comment I was responding to however claims that some people will continue to mine at a loss after the subsidy is negligible. However that assumes that people would be willing lose hundreds of millions of dollars per year on power costs just to meet current security levels, let alone whatever level of higher security might be required in a moonshot scenario.

Millions of people collectively losing hundreds of millions of dollars a year is less than $1/month individually.

Sorry to be pedantic, but I do believe the daily cost of mining is closer to $250,000 - $750,000. Not a small number, but also not millions per day.

I'm a physicist so naturally I do all back-of-the-envelope calculations to one-significant figure with rounding at each step. :)

My own estimation is between $400k per day (hard lower bound) and $800k per day depending on assumptions about hardware efficiency, although around $100k / day was added in the last week in a trend that is continuing, so $1MM/day will very quickly be accurate.