Aside from the ASICs themselves? Cheap, if he can get a large board run together. The real questions are, how much for the ASICs, and are you capable of mounting BGA.
This would be a really easy board to manufacture. Low unique part count. I just need to move the decoupling cap vias out of pad and it'll be ready.
KnCMiner is the only competitor who has 28nm chips, but their chips are merely 1000 Mhash/Joule, which is a power efficiency pretty close to Avalon gen2: 730 Mhash/Joule.