Difficulty is crashing now. I went through this last year when the price was dropping and thus making mining unprofitable for everyone. As it hit $4, I thought I'd have to turn off my miners, but the difficulty kept dropping, keeping me riding the profitability line. I was on both sides at different times, but I didn't care that much since I was also mining for principle and support of the network. I was never more than 10% unprofitable. From that it seemed to me that most GPU miners either paid more than I do in electricity (11c/kwh) or they didn't have cards as efficient as I (1.42 MHps/W measured at the wall). That system right now would be -1.5% profitable which in past experience has people turning off their rigs.
Wow, do you undervolt your cards? I've tried undervolting but wasn't successful. Mine is 2.3 something, much worse than yours.
