I think you're calculating that incorrectly. If you bought two Jupiters for 58 BTC each, or 116 BTC, and you've mined 37.5 BTC, then your ROI so far is -67%.
I do think KnCs stand a chance of having a USD ROI. At least I hope so since I have one (and paid USD for it, USD I wasn't planning on buying BTC with). Will they ROI in BTC? I'm not sure.
Both KnC and Hashfast units might ROI over the long, long term. But KnCs will have a huge head start, hopefully covering most of their initial cost before HF even ships.
I'm not in the camp of BTC spent to BTC mined for ROI.. There was no way to buy ~15000 worth of BTC on 0% interest credit cards so it is a moot point. I won't generate any interest on my purchase until next June so your cost basis may vary.. and that will be 2014 dollars not 2013 which we all know inflation reduces that as time value of money with fiat (small but valid)
I was hoping to get more than half in cash value in the first 30 days, but missing that first week of October was a lot of coins left on the table. But I am still one of the lucky ones to get it one week in.
Hopefully most of you are in the front of the line for HF