I have heard that Saab could have built the best version of 9-3 for the price of the cheapest 9-3 if they only had one variant of everything. Not sure if that is true but increasing the number of variants is increasing the price. It’s not only about the cost of the part, it also increases the workload of the design, purchasing from supplier, testing, factory and aftermarket.

So I’m not surprised that it is cheaper for BMW to install it in every car.