2021 Ram 3500 H.O.

Designing and manufacturing a fuel system is a lot more complicated than most think. Not only dos the R&D cost a lot of money, but so does the certifications/standards required. Since it is an emissions component or system, you have to attain and/or abide by many different certifications/standards wherever you sell an engine with this system. These certifications/standards will change from one region or country to the next, and a lot of it is more political than environmental. Then you also have more liability as well.

This is a major reason why almost all(if not all) diesel engine manufacturers from BMW to Cummins don't make their own fuel systems. It is not just a diesel thing either, most HPFP fuel systems on the direct injected gas engines are made by Bosch or other suppliers as well.