So for what the $450 the board you link costs, plus $50 for CPU and another $50 for memory, $550 total (low cost miner build components) you could build 3X the typical boards.
3X Biostar TB85 ($65 ea) $195
Except you can't because the Booster TB85 is out of stock at Amazon and NewEgg. Which is not surprising since it's 2 generations old at this point.
That's the purpose of this thread-- to find Z170 or Z270 boards that can drive 6GPUs.