You have to be fucking with me right.  They are automated assembly machines.  We are talking a half a second (conservatively).  It isn't like these are hand soldered.  The assembly house is going to crank out thousands of boards a day.  If KNC had a big enough run a good assembly house could do tens of thousands of units per day.  The automated board construction isn't the bottleneck, it is the rest of the mundane manual stuff like bolting down boards, connecting wires, and mounting heatsinks which takes a "long" time.