(OP here) the $700 was for 50 arm boards and 5 hub boards, fully assembled and shipped including all the parts (enough for 2 full arrays, with some spares). $350 @ qty 2 is pretty good, considering just the microphones is ~$100 for each array!

Unfortunately the assembly/DFM didn't work out well, but with some better design and foresight it should be much less work/wiring compared to wiring them manually.