Bitcoin Forum

Lets get ready to hear an opinion from someone who has no idea what their doing.

INTRO
I've done some rudimentary math here, but it seems like in most cases that usb block eruptors actually will ROI (contrary to popular belief), considering their low purchase point in that big group buy by CanaryInTheMine. Unless difficulty can sustain 35% growth per month--forever, I don't see how you can lose money here.

ASSUMPTIONS

-I live in Ottawa, so my power costs even out to 0.08/kwh.

-I order 15 block eruptors for 0.33btc each (I pick them up from the states and bring them across the border to avoid international shipping. I'll have to pay 13% HST when I declare them)

-Difficulty increases by 25% monthly from a starting difficulty of approx. 50 million (Which is the estimated diff at the time said block eruptors will arrive)

-I can get it all running within a week of ordering.

Total Theoretical Hashrate: 5.04 GH/s
Total Cost: $495
Time to ROI: 27 weeks

Even at a difficulty increase of 30% monthly, it still hits ROI at 34 weeks. What am I missing here?



Here's my source if you were wondering:

http://btcinvest.net/bitcoin-mining-profit-calculator.php?diff=49873855.03985008&dcosts=495&diff_mincrease=25&blpbtc=25&dhsmhs=5040&btcusd_mincrease=0&btcusd=99.96&dpowcon=42.5&dleadtime=1&pcost=0.08&calcweeks=55&action=calc# (http://btcinvest.net/bitcoin-mining-profit-calculator.php?diff=49873855.03985008&dcosts=495&diff_mincrease=25&blpbtc=25&dhsmhs=5040&btcusd_mincrease=0&btcusd=99.96&dpowcon=42.5&dleadtime=1&pcost=0.08&calcweeks=55&action=calc#)

It has lately been more like 30% per 10 days.  So run your numbers again with 75% increase per month and another worst case scenario of +100% per month.

You aren't missing anything.  If difficulty rises as slow as you predict you will be profitable but if difficulty rises faster, much faster ....