alt Hacker NewsExactly: "The average production cost was sitting at $88,000 per bitcoin in mid-March". Emphasis on average. Just as in a free market, those miners with higher mining costs are priced out of the market. Or are pressured to become more efficient. Those that are below-average probably already are efficient.
You left off the critically important part of the quote, IMO...
> ... according to Checkonchain's difficulty regression model
It's a guess based on oil costs (as a proxy for energy costs). Personally I think it is completely worthless.