This is wrong argument. Mining costs are different for different miners. Someone has cheap electricity, someone has cheap electronics. If mining is not profitable for some part of miners, they'll stop mining and difficulty of mining will decrease, making mining more profitable again. It's a self-regulating mechanism.
>If mining is not profitable for some part of miners, they'll stop mining //
Real world is always more complex than this.
My expectation would be that done miners will contribute to mine at below profit levels because they seek to cut their losses.
If they have cheap electricity but large sunk costs due to expensive hardware, that's not paid off, then - absent other uses for the hardware - they'd seek to reduce the loss?
So mining wouldn't stop, but it would drop off precipitously.
There is a level below profitability but above electricity costs where most professional miners will keep mining. But at some price level miners start dropping out because the electricity is more expensive than the mining income.
Luckily this wouldn't be one huge even but dragged out over a large price range since electricity prices vary considerably depending on location and source. This ensures that there is enough time for difficulty adjustments to kick in and correct the market.
