They are most certainly using cheap labor to design, plan, operate and maintain those "dark" plants. Very highly automated production lines (cars) have similar

They are most certainly using cheap labor to design, plan, operate and maintain those "dark" plants. Very highly automated production lines (cars) have similarly moved along the labor-price gradient in Europe (~east) during the last decades, despite language barriers: You need some engineers, electricians, constructions workers, janitors, etc regardless, and those still scale with general labor costs, even if there's no human hands in the assembly line.