Pcb manufacturing is cheap. I put 20 parts 1.5 inch by 24 inch into pcbway and ended up with final delivered cost of 240 dollars.

Not having to deal with wiring that many individual boards and all days of headaches tracking down issues is well worth it in my book.

Huh, you're right. I expected 24-inch-long PCBs to be quite a bit more expensive, but even 4-layer boards at those sizes are still available at discount prices. I guess such thin boards could be used to fill in edges of mixed-order panels? It does make me wonder why they say "the array" was $700. Maybe assembly was extremely expensive

It doesn't seem they weren't really able to benefit from it all that much, though: half of them arrived defective, and they had to do quite a lot of debugging to fix them.