How is it that everyone is using the term ROI so incorrectly? ROI = (Gain from investment - investment) / investment. The answer to that equation is not months, it's a percent. The time it takes to break even or recoup costs is not ROI.
ROI as "misused" in the cryptocoin mining industry is generally a time estimate to get enough payout in coin value to match the price of the hardware.
DO keep in mind that most cryptocoin miners are not financial professionals or experts.
It also tends to ignore the residual value of the underlying hardware - which in the case of ASIC miners wasn't a particularly bad choice as those often had very little value left by the time they have earned more than their own price, prior to the current 14/16 nm generation,
Would like to be able to get some money back eventually.