That price is outrageous! Even with free electricity (and assuming a 15% ave diff increase) it will produce less than 2 bitcoins over its lifetime. Thats right, wont even 50% ROI with free electricity.
I truly feel sorry for anyone dumb enough to buy this machine at those prices.
There won't be a 15% average difficulty increase for long if BTC stay at this price. Sure there's a bunch of hardware already paid for, but you can see the reason why in the last two pages here, and in your post. People are not going to purchase more mining gear unless the price goes back up.
Even someone paying 6c/kWh and 0.5J/GH gear would be spending everything he earned on power at 240B difficulty, let along paying down the money he used to purchase it. That would happen in early March with a 15%/jump increase. The question is though, at the end of December when the difficulty is 105B (@15%), who is going to be buying the equipment to keep the rise going if the price isn't moving up? At the point somebody running (not yet produced) gear at 0.35J/GH with 0.15c/kWh power will make less than $1 per day per Terahash/s. Even the guy at 6c/kWh is only making $1.5 per Terahash/s.
Even with cheap power, no one will be buying @ 100B unless it's <0.5J/GH and <$0.2/TH/s. That's $400 for an S4, and while they might sell excess inventory for that price they can't produce an S4 for $400, let alone less than $400 shipped and make a small profit.