Where did you get the info that S3 production cost is 0.4$/GH? Hopefully the production cost is cheaper for S4.
It might be a little lower as the chips are overclocked and no PSU is included, but not by much.
It is accurate for S4 though (more chips, included PSU...).
But where did you get the $0.4/gh from?
Each unit also includes shipping costs which aren´t cheap at all, so the profit for bitmain is very thin.
I have to disagree. Shipping from china to USA is only ~$5/kg.