People who say anything about not meeting ROI are ignorant. How can you comment on ROI when you have no idea what the cost of bitcoin will be next week, next month, etc.
mpark the proper way to factor ROI on any miner actually doesn't involve the conversion price of
BTC to some other random currency. If you pay X
BTC for a miner and in it's life it generates >X (plus costs) then the miner profited. If you buy a miner for 1
BTC when it's at say $500 and it makes .5
BTC but the coin doubles to $1k have you broken even? If you believe you have you are allowing yourself to be blinded.
I am not sure that this calculation is correct since you did not start with BTC in the very beginning, but typically had earned $$, euros, etc.
Your electrical costs are also in $$ and euros.
Debit: your fiat used to buy BTC to buy a miner plus the cost of your electricity.
Credit: price that you sell your used miner minus auction expenses and postage plus your earned BTC.
First, subtract $$ credits from debits=residual cost
Compare your residual cost with BTC that you have earned by mining, which would indicate how much the earned BTC cost to you. If this number is lower than the average BTC price between the start of your mining operation and ending of mining for this piece of equipment, then you made a positive ROI.
Of course, if you never sell your used equipment, then you will have to compare your earned BTC with the $$ cost of initial outlay plus electricity.