There is some scale level where you've captured all the manufacturing efficiencies (e.g. the asicminer boards in those pictures are only 10GH/s per board), and

There is some scale level where you've captured all the manufacturing efficiencies (e.g. the asicminer boards in those pictures are only 10GH/s per board), and once you've crossed that it's generally more efficient to distribute the hardware because you can make better use of low level waste heat as home heating (or at least not having to actively cool it).