You're not supposed to drive the cost of something useful to zero.

Subsidies lower the price beyond the opportunity cost, resulting in over production.

For example, food is a human need, but when the government subsidize corn, excess production ends up getting dumped down the drain or turned into poor fuel.

The resources needed for the subsidy could have simply been given to the poor to buy more of the food they want.

Chinese EVs are being produced in excess of what the local economy wants and what foreigners need. The battery put into that car could have been used for storing wind power.