PCBs and CNC milled or 3d printed parts are a bit of an exception in that the processes and services are stadardized enough that replication is not that hard u

PCBs and CNC milled or 3d printed parts are a bit of an exception in that the processes and services are stadardized enough that replication is not that hard unless something really crazy is going. But everything that relies on more traditional mass production methods (injection molding, casting, ...) is much more dependent on the actual execution of the manufacturing process and the part designs will generally accomodate that, for example by avoiding certain geometries or incorporating ways to account for manufacturing tolerances during assembly. I am not an engineer myself, but I had to work with mechanical engineers occasionally and I learned that the amount of work that goes into making some seemingly simple parts manufacturable at scale and at cost can be surprising.