Although I agree, making a one off is WAAAY different from going into production. A friend made a *KILLER* rifle rest, and was trying to make more of them. He gave up - and I wanted one! I myself make a reproduction ancient Egyptian musical instrument called a "Sistrum". The first couple were easy, then I had to design for manufacturablity, and there's *always* something. Suppliers changing the FFF (Form, Fit, Function) of the components involved, having to source alternates when a component is suddenly not available from where you've been obtaining it, getting raw materials of the correct specs, etc, etc, blah, blah, blah...
The bumper is certainly worthy of production, but its a headache. That's why they're so darn expensive!