How does that even begin to make sense to anyone? They don't sell for cash, they sell for BTC, so whether you pay in BTC you have, or pay cash for new BTC then pay in BTC it's exactly the same thing. If the blade will never ROI in BTC, how does it matter whether you used $ or BTC - just buy BTC and keep it.
Back to the topic at hand, future diff increases are impossible to predict, but obviously the device is very very unlikely to ROI. What's easier to predict is that morons will buy it anyway.
see goxed post
https://bitcointalksearch.org/topic/m.2696744
Parroting other people's ideas doesn't make them true.