Most of the cost of batteries is in labor? So why not outsource them out of China where labor is quite expensive vs developing countries?
They are actually importing Chinese workers to their Brazil factory, leading to the slave labor expose by Brazilian authorities [0]. They have the same trouble recruiting in Thailand, where workers have functioning unions and enjoy modern working rights, instead of 19th-early 20th century Industrial Revolution type stuff.
[0] https://en.wikipedia.org/wiki/BYD_Brazil_working_conditions_...