It's not like we are talking about buying gears off of Alibaba. We're talking about buying gears from an established vendor with a reputation to protect. The first set of gears I bought were Yukons and they were some nasty loud gears. Yukon came out with a statement at that time acknowledging that fact. That's what reputable vendors do. I'm not about to worry about the metallurgy of their product because the country of origin as a whole isn't up to some quality standard.I don't know if I'd go quite that far: Japan was really good by the 70's even if half of the west wasn't ready to admit it yet. Korea is pretty much there. China is a step behind that, but they're getting there. The trouble China has (in my opinion) is their industrial culture doesn't have quite the focus on quality yet. They're perfectly capable of making really good stuff, but QC isn't as thorough, so you have to be prepared to do some of that yourself. The manufacturer can be the force behind that, but there are always growing pains. Nitro may have a good handle on it by now, but those hardness failures that were mentioned upthread are exactly the kind of thing that I've seen in all sorts of different industries.
I have a level of expertise in materials testing but I don't have the tools at home to check alloy composition or hardness to make sure a bad batch didn't get through. For similar money, I have more faith in Korea at this time.