Added columns with $ 
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So if eth's reward downed on near 40%, then earnings in $ fell by 20% for 14 days!!!
Who asked you to go through all this? That isn't even accurate and their is no way you can keep a 100% accurate data about mining reward and difficulty lol, it's like suffering yourself for nothing, do you even have a mining rig or you are just here to create mining FUD So if eth's reward downed on near 40%, then earnings in $ fell by 20% for 14 days!!!
And eth is at an all time high of about 3300 and viabtc rates are now
holding steady at $.1054 an mh
It is hard fighting with naysayers.
But I sometimes try to point out the math.
at $ 0.08 an mh a 3080 makes $8 usd. it burns $1.20 usd at 20 cent power or $6.80
so 365 x 6.80 = $2482 paid back after power.
at $0.09 an mh $2847
at $0.10 an mh. $3212
at $0.105 and mh $3394. we are at this point
so we are fine to mine a 3080
if we drop to $0.05 an mh and stay there the op has some correctness
as a 3080 at 20 cent power pays back only 1387 a year. So if you paid 2500 you would be nervous.
but we are at $0.1054 and mh so no worries yet.