Why else would they come out and say it is costing them significantly less than 400 to mine coins, they are trying to drive out competition by crashing the price. They are hoping to starve you boys out.
Being able to mine coins cheaply has no effect on the price. It just means they can take more of a share of the block reward, driving up the difficulty and driving out less efficient miners.
f you want evidence.. lets say KNC expanded to 10% network hash.. that means a maximum of 360 coins a day.. just looking on BTC-E for instance about 360 coins only changed the price by $5 at most. and that was in a 1 shot dump. and the next hour the price was back to where it was
The 360 BTC they mine in your example doesn't increase the volume because they are taken from other miners who already would have been selling.