IMO, the current value of a bitcoin has nothing to do with the cost to produce it or it would be in the $10-20 range, and that would still be a profit for the majority of people that mined them.
Plugging in the numbers, the 7750, which is the most energy efficient of the GPUs listed, needs a $25 price to break even if the hardware is free. That assumes a $0.15/kWh energy price, so if the majority has electricity in the 7-12 cents/kWh range you might be right.
Bitcoins in a rational market would cost only as much as they cost to make with perhaps a small premium.
They are probably mined as much as is economical to do. The main sign that this is happening is that mining without the latest generation of GPU is uneconomical. Any short term speculation that drives the price higher just makes it a better deal to mine more.
At the other end it's easy to imagine a situation where bitcoins aren't useful enough to be worth mining and the price drops below the cost to make them. As long as they're convenient for illegal transactions this won't happen.
You're at Witt's End.