And what do you buy bitcoins with?
He's right. The initial cost is in flat not BTC which you've had to buy or obtain in some way that cost you flat.
I could just as easily say that I could make more trading BTC with leverage, or trading gold....but that's not the point, nor the topic of this thread...it's about KnC Miners and mining.
The initial cost can be fiat or BTC, since KNC accepts bitpay. If a Jupiter is 60 BTC and you don't think it will pay back > 60 BTC then you shouldn't buy one.
Keep in mind, a lot of people are using bitcoins that they got from GPU mining, and are investing in order to increase their BTC holdings.
Some people are investing in USD in order to increase their USD, and may just sell all the BTC they mine. Other people are investing in BTC they already have and want to increase their BTC holdings. For the second group the price is irrelevant as far as their ROI is concerned.