Aerospace isn't necessarily like that for a number of reasons. A large driver of cost is quality control. For example, when a custom part is manufactured it nee

Aerospace isn't necessarily like that for a number of reasons. A large driver of cost is quality control. For example, when a custom part is manufactured it needs to go through a number of tests, some of the raw material needs to be kept and tracked for future testing, etc. When they get shipped they have to be be tracked and handled differently, sometimes accelerometers are placed on the cargo to measure any shocks, etc. They need to be stored in a bonded warehouse, often climate controlled throughout its life. All of that control, testing and documentation adds to the cost even after R&D is a sunk cost.