Important fact is that the whole automotive industry is built on heavy outsourcing. Typical car manufacturer only manufactures the car body, maybe engine and does the final assembly. For everything else not only the manufacturing but also R&D is outsourced.
Also, motor manufacturers design basic platforms that are used across many models and often across many brands. A basic chassis, engine and drivetrain package might be the basis for a dozen different cars. Developing a platform might cost hundreds of millions of dollars, but those costs can be spread across several million cars.
Was going to write exactly this. Open the hood and you see Bosch, Denso, Delphi logos, not the OEM. The car maker makes maybe the engine, and even that is increasingly outsourced.
