I can't answer most of your comment's questions, but to just answer the first point - it's about cost of labor.

Tata motors are made in India. BYD is Chinese. Both involved much lower cost of labor, both from the engineering perspective and the manufacturing too.

Heck, even Tesla themselves have a factory in China and from the most recent figures I could find, their Chinese built Tesla's are 40% cheaper than the American built Teslas -- https://financialpost.com/commodities/energy/electric-vehicl...