They are so cheap, infact, that no other country in the world is able to compete even with huge tariffs.

They are not cheap. They are extremely efficient at manufacturing. The 201st panel look exactly the same as 1st one. Definitely no human labor involved. Huge well readable serial numbers placed on multiple places of the panel for camera based identification. Usually no single failing panel in shipping container. The bad ones were clearly damaged during transportation. This efficiency looks scary when I see output of my workplace in Germany.