Man, you would think that some manufacturing company would set up shop right next to them, use some automated machines to make this process more efficient and put this "shop" out of business. Wait. the North American rotor manufacturers had automated equipment decades ago and they've all closed up and moved outside of the borders.
It must have been 15+ years ago, I needed a front rotor for my Dodge Dakota pickup. Having a little time on my hands, I wanted to find a rotor that was made in USA. I looked at several chain stores and none of them had one. I remember the O'Reilly's manager even let me look at his stash of replacement brake rotors and all of them were made in Mexico. (At that time) Finally, I found a one-man parts store that had a shop that had been in his family for decades. I told him what I wanted and he checked his parts book and I remember it was a genuine book. He took a rotor off the top shelf that was a different brand than what he was currently selling (he'd gotten in trouble with a couple of previous suppliers, but that was another topic), blew the dust off the box and had me look at it. It was labeled as being made in Canada and that was good enough for me. A year later I needed the other front rotor and I didn't bother to shop around for anything locally sourced. At that time, I believe it was the beginning of the wave of Chinese-made rotors.
This one man shop has been closed for about 7-8 years now. It was in a town of 2,500 and an O'Reilly store that moved his forced his closure.