Why are solar panels and batteries from China so cheap?

It's more to do with automation and state-of-the art manufacturing processes than cheap labour.

Sustainability by numbers
Bluesky

Bluesky Social
China’s dying EV batteries are powering its circular economy in new-energy era

Recycling critical materials such as lithium, cobalt and nickel are driving profits and shoring up China’s resource security as trade war with US hits supply chains.

South China Morning Post