It would have to go down further to be not worth doing, since he covered the cost in ten days, and the electricity cost is less than $2/week. At $7/week for example he would roughly break even over a year even factoring in the cost of the device.
Yes, but (a) the decline / rise of difficiulty will continue, and (b) there's a year long waitlist.
You can make more money playing the ups / downs of btc (for example, right now, there is a down explicitly because gtx halted US dollar transfers so everyone is panic transferring BTC out and selling it off). Than trying to invest in a btc mining rig and playing a literal lottery with computing hashes, or joining a mining guild and making very little very consistently.
Which raises the question: what's the breakeven volume for Butterfly Labs customers? As more and more people buy their miners, how does the time to recover its cost dilate?
The main problem is that the waiting list is currently almost a year. If you order a miner today you won't see it until 2014.
What about the ones on Ebay for $500-1000? If the breakeven is so good, why wouldn't those people just plug them in?
They probably are plugged in while the auction is going. But with each day the resale value decreases as well.
It's $20/day though, not $20/week. At that rate, if you can grab one right now, you don't really have anything to lose; you will have recouped your investement in about 3 weeks, maybe 4, and everything else is extra.
Sounds like they already recouped the cost of the miner. So if power consumption is $100/year, they need to make at least $2/week.