In short, mining difficulty and costs DO NOT affect bitcoin prices. At least not in any significant way.
I see it bit differently. With so much invested in Bitcoin ASIC, the owners are not likely to sell quick because they woudnt get investments back anyways, thus price might be rising
I feel the same way. Since selling the coins right now is hardly enough to break even with the ASIC miners, people will tend to hold on to them. That would mean that less coins being sold and produce a higher demand for them causing the price to rise.
First, people have to pay for electricity, so they can't ask their power company to hold off on sending them a bill until bitcoin prices rises a bit. The way it works is, if it's profitable to mine, more people buy ASICs and start to mine. If it's unprofitable, those miners are far better off shutting down their ASICs and using the money they would've paid for electricity to buy bitcoins directly; why spend $100 to mine $90 worth of bitcoins in hopes their price will rise, when you can just buy $100 worth of bitcoin? In that sense, the price rises and falls on it's own, and the difficulty just follows it up and down.
Second, the reason I say miners don't affect price is because the amount of mined coins that are being sold every day is not a big percentage of the total amount of coins being traded. The percent has gone up recently, due to the decrease in trading, but something like 3% to 5% of coins being added to the market won't move prices too much. It will put a constant downward pressure on it (which will be constant and will not change due to difficulty changes, since number of coins mined doesn't change), but it's offset by the upward pressure of new adoption, and so the actual mining, or difficulty, doesn't really matter much.