I read your reasoning about the cost of mining bitcoin. And it seems to me too that right now anyone has a good opportunity to buy cheap bitcoin. But what if there is an energy crisis in the future, as some say. What if the big miners leave the field and sell the mining equipment. It could happen that the difficulty of mining would drop. Then the value of bitcoin will drop too. Especially since there will soon be a new halving, and at the usual cost there will be half as many coins mined.
the hobby miners that change their minds daily will drop first(they have the highest costs anyway)
this then means there is less competition and more coin to give to the large industrial efficient miners. thus bringing more coin to those base cost miners. which then balances out the industrial miners larger costs.
larger mining cost would increase. but not at a fast/large swing compared to the hobby miners
at the halving yes coins rewarded halve and the competition game happens again
this is why you see asics get more efficient
in 2016
2.8kwh only hashed about 9thash..
in 2017
2.8kwh only hashed about 26thash..
in 2020 now this december
2.8kwh hashes about 130thash..
thats a 3x then 5x efficiency gain in 6 years
meaning the halving effects of 2016 got taken care of and also the halving of 2020 got taken care of