Citation needed. Yes, the many Chinese manufacturers are fighting each other... but I see no reason why they can't maintain prices. And I doubt they're all unprofitable, especially the big ones like BYD.
The magic is not in am i making a different widget. Its how that widget is made, what are all the machines involved in making that widget. Could i design a machine to make the exact same widget, but with reduced vibrations, 10% less electricity, and reduce maintenance by 10% while still maintaining quality?
For example
If they see a company making widgets, and this company makes them by using 10 custom engineered machines with a lifetime production run of 5 each, each of these 10 custom made machines needs to be designed by a army of engineers working for years.
A competitor in china will do espionage, the CEO's and upper management will study these 10 machines in depth, see where they could make improvements and if they see a opportunity like hey machine number 3 , 7 and 10 are designed like X, if we design it like Y we could cut electricity consumption by 10%. This will allow use to undercut their widgets for 10 cents.
The people running US corps are all business bros, and the people are lazy, they aren't interested in doing years of labor, to make a production line of 10 machines to undercut another billion dollar company for 10 cents.
If you go to your local chinatown, the chinese restaurants operate this way always constantly looking to crush their competitors, always trying to improve supply chains, always looking to cut costs and undercut competitors. Looking to cut out middlemen.