A bird in the hand is worth two in the bush.
M
Your BTC is the bird in the hand, the USB sticks are the birds in the bush.
Ouch when difficulty just hit 19 million. The block eruptor is now making just $0.75 a day (0.0078btc) at current prices. Forecast 1 year from today now is to just make $90 profit in total if the price remains around $100/btc. This means in 12 months from today this usb stick will not even have mined 1 btc, despite costing 2btc+, with difficulty rises of 30% a month or more.
These are turning into a far worse deal quicker than i imagined!
M