When this is intended as a bitcoin miner, why the 6 layer pcb?

Heck, I can imagine it would be doable on a double layer board with minimal I/O, if not even single layer if the power for both chips can be supplied by a single power converter. The thing I want is a pcie card with nothing on it except 2 fpgas, and the power circuit.

I am willing to bet this can be done with double layer and around USD 1/mhash.