I have not had enough sleep for days, but I don't think my math is that bad, 15.5 to 21.4 means we had a 5.9 hashrate increment, if not for the halving we would (in theory) have had double that which is 11.8, so 15.5T + 11.8T = 27.3T  or 76%. I think your mistake was multiplying the total difficulty of 21.4 by 2 to make up for the halving, keep in mind that 15.5T of that is the old difficulty which has nothing to do with the theoretical new difficulty, do I make any sense?


IIRC Q1 2019 was when bitmain got rid of all the S9s they had, the majority of them must have been made prior to that, I highly doubt they made 400,000 in 3 months, also, it was probably easier to make those S9s compared to the S19, seeing that a whale like RIOT blockchain has to wait until October 2021 for a relatively small order of 37,000 miners to be fully delivered suggests that Bitmain is nowhere near making half a million miner in 2021, but well, as you say, they will want to make it work and they could find a way.


Given the current situation, I would be very surprised if we hit 40T by Feb 2022, however, this is the lowest number one should expect just to be on the reasonable safe side.



If I was going to buy a mining gear tomorrow, I'd just assume that we will at least hit a 100% difficulty increment every year, bitcoin price will not go past its current levels and my gears will die in 12 months, and then I'll run the numbers based on that, so if, with the assumption that my new miner will make half the profit it makes now and can't ROI before the end of the year, I won't be buying that gear.