The expensive part is creating the design for a part and writing the program to cut the piece out of a $2 chunk of aluminum. Once the initial work is done, these things could be produced for next to nothing. If some enterprising individual with access to a CNC milling machine could take the time to do this and produce a better quality product, I'd be willing to pay what slides in country are going for, rather than having to take a crap shoot as to whether the metal part I'm ordering is actually going to fit my gun without requiring a shitload of mods to make it work.
How about if someone were to machine high quality hardened gearboxes? Again, I would be willing to spend a few extra bucks for a QUALITY product produced in Canada. I' sure someone could give Systema a run for their money on replacement AEG internals if they tried.