The Mining Factor chart (in green, above) published by BitcoinX shows mining revenue received over a 24 hour period for each 100 MHash/s of capacity. An typical $1,800 rig producing 1.4 GHash/s then will, at current levels, bring in about $8 per day of revenue.
That level means mining can still be profitable versus the typical $2 to $3 of electricity consumed by the hardware to churn out that 1.4 GHash/s. Compared to the profitability levels seen in May and early June, however, those hoping to pay off their rigs after a few months are going to be frustrated – for a very long time.
Some miners have dropped out of mining recently due to the low price levels and/or the discomfort caused by the heat and noise from the rigs. But the difficulty level will likely stay flat without much of a rise or decline as those who are more efficient or pay a low amount for electricity are still adding enough capacity to offset all those calling it quits.
Among those rigs classified as being the most efficient are those with 2X6990 and 3X6990 configurations. Supplies of the 6990 has been extremely tight though AMD has beefed up the production line for these graphics cards and stocks of these cards will likely be getting replenished soon.
Unless the Bitcoin exchange rate heads back up, those with higher utility rates and those mining without the best performing hardware are likely to start heading for the exits, if they haven’t been shaken out already.