If Mining BTC Even with free electricity cannot pay the mining equipment in a year, that will be the doomsday of BTC, 2000$-2500$ is the limit.
Use your head once in a while! When Bitcoin was in the bear market of 2016 with prices below 4000 miners were also below the point of profitability with no way to pay off equipment bought in 2014 for $600 and more. Did that destroy Bitcoin? Even if we repeat 2015 and 16 worst thing that can happen is another 6 months of bear market and maybe 4000 dollar low