I think you are not factoring in the cost of FPGAs.
That's a good point, but the FPGA market looks totally dis-functional to me. I suspect that pricing practices will change as the impact of the Intel/Altera acquisition works thru the system.
I doubt it. Altera/Intel have no desire to erode their margins, and there are a lot more high dollar uses for FPGAs than mining.... Most of the companies I've worked for will spend $50k-$100k per FPGA, for hundreds of engineers, to pull in an ASIC design schedule.