to be honest man, if the bitcoin mining fever was not on, they would not sell it or even manufacture at all. nobody is gonna use the USB miner as people are using the GPU miners instead AFAIK. unless bitcoin is far higher in price which leads profit via USB mining (selling them for certain profit
), IMO your USB miners are dud.
edit: don't worry, if you have low electricity bills, mining with them are profitable
we're in the bitcoin mining subforum... I would probably agree with you if we talking about altcoin mining, but if you're talking about BTC mining, even an usb miner would beat GPU mining every day of the week.
Eventough the list of non specialised hardware for BTC mining hasn't been updated for a while, i think it still makes sense to do the math
If you look at
https://en.bitcoin.it/wiki/Non-specialized_hardware_comparison#AMD_.28ATI.29A rig with 6 x AMD 6870 produces 2.5 Gh/s while consuming 1200 Watt.
The price of one card is ~€200, the price for a PC, risers, PSU,... will likely be over €400. The sum of this rig would be €1600
ONE geccoscience compac runs at 8 Gh when underclocked, it consumes less than 6Watt. It costs €50
It can be controlled with a rPI, setting you back €50, using 3 Watt
https://www.bitshopper.de/shop/sha-256-miner-en/gekkoscience-compac/?lang=enWhen we compare both, using FREE electricity:
The GPU rig:
https://www.coinwarz.com/calculators/bitcoin-mining-calculator/?h=2.5&p=1200&pc=0.0&pf=0&d=860221984436.22200000&r=12.50000000&er=2764.06270000&hc=1880at current diff, block reward and btc price, you'd ROI (pay back) your rig in: 930714 days (that's ~2500 years)
The compaq:
https://www.coinwarz.com/calculators/bitcoin-mining-calculator/?h=8&p=6&pc=0.00&pf=0.00&d=860221984436.22200000&r=12.50000000&er=2764.06270000&hc=100break even when everything stays status-quo: 15470 days (that's ~42 years)
If you add a power price of 1 cent/Kwu, things get even worse for the GPU rig.
So, to sum it up, if you GPU mine, you'll break even when all wars are over and the planet has been reduced to a barren wasteland, only in 100 generations will your investment in the rig be payed back (in case the diff doesn't rise, the price doesn't fall and the block reward would magically stay the same)/
If you mine with a recent usb miner, it depends on your age, but there's a decent chance the usbstick will have payed for itself by the time you kick the bucket