Do you actually think building to spec is actually HARD to do?? If it is then they shouldn't be in business. Again this isn't rocket science. We're talking about a light assembly.
I haven't had to buy a new headlight for my 4runner...but I did have to buy a rear tail light after it was hit by an idiot in a parking lot. Light assembly from dealer was at least twice more then what I paid for...the aftermarket is PERFECT. I defy anyone to tell which one is the OEM and which one is the aftermarket.
As I said..there ARE junk parts out there. Never said there weren't. But that doesn't mean they all are. It may be tough to find the better aftermarket parts. Usually they can be found at the better independent parts stores. Maybe I'm lucky in that I've always lived in an area that had them. Here in NH we have a few...I usually buy at either Robins or Sanel Brothers. Only thing I buy at places like ADAP is Car Wash and wax.