actually you can have rough computation on how much you can earn daily after the block halving, just divide to 2 how much you are getting per block found and you will still have some small profit out of it
Yes that what i am saying if you current you getting 10 usd daily then after Havel you will get $5 approx ..as current the efficiency is around 40% so after Havel it may be almost 70% so you have quite low profit and reward is less maintenance is high