Considering they'll make over $100 each in the next seven days we will accept no bids under $700 each. Otherwise we're much better off running them into the ground. Yes difficulty rises are getting much larger but if you look at the last ninety days difficulty increase ratios are getting smaller. Just like 200% rise of 50 is 100 and a 100% rise of 100 is 200. So even the jump in the example was much bigger to 200 the rate of change is slowing. You should factor that into to your profit calculations on them. Plus bitcoin prices are rising and we accept USD and GBP bank transfers.
(just because I hate "rough estimates" without supporting math -- as of 10th Oct, 2013)
5.4 days till diff adjustment. Round down to 5 days since we've seen spikes well over 2PH numerous times in the last week/two.
$167.71 USD according to "bitaverage"
Daily production for a single 54-62GH single is approximately 0.1 btc a day, or 0.5 btc between now and then. Once diff adjustment hits, daily output drops to 0.08 btc day, so you'll rack up another .16 btc, for a total of about .66 btc over the next 7 days, or $110.69 assuming price stays static.
Next diff jump will coming another 10 days later so you'll earn another 0.8 BTC, for a grand total of 1.46 BTC, or $244.86 over the next 17 days.
The next diff jump beyond that one will likely drop your earnings into the 0.06 btc day / $11.26 day range.
Quick math says that if you had the box, in your hands today, you'd make --about-- 1.46 + 0.72 btc, or 2.18 BTC over the next 30 days, or $365.
The diff jumps AFTER those start getting into CRAZY Cointerra/BitFury/etc/etc shipping, and your single will make you less than $100 a month quite quickly. And your ROI's get MUCH worse if the price drops back down into the $120 range where it was a short time ago.
My Point to all this? A BFL single @54-62GH isn't worth $700 today.. It's worth about $300, and $200 next week. Because VERY VERY soon, Cointerra/others hardware, shipping in the $3-5/GH range will be in peoples hands.. and that's what you're trying to compete with when you're selling yours.
