It used to be easy to calculate the days to break even on a miner and make a decision to buy or not.
False. We only thought our calculations were more accurate. Now we know that calculations are just about guaranteed to be way off.
Were not accurate because it was hard to say what is going to happen with a difficult - hardware and other stuffs
anyway bitcoin mining is still profitable and miners cant say that it is not
(if they got nice rigs)