Generally speaking, Japanese culture is to do things fanatically well -- even at the expense of profit. So it does not surprise me that some Japanese tool companies are next level in terms of tolerances, materials, etc. In the USA Snap On charges a lot for the service and because they can (people buy). So they probably see no reason to cut their profit.
My comment on Japanese culture comes from the basis of me working there some over the years. My wife is Japanese also and our sons are 1/2 Japanese and go to school in Japan in the summers. So I see what I say fairly clearly. It is not a universal rule that Japan is high quality -- but it is mostly true. Globalization has also impacted Japan less since Japanese are so picky and it is considered dishonorable to do things poorly if you have the capability to do better. So you generally get more for your money in Japan -- especially recently with the US dollar very inflated in Japan.
I would be willing to bet that Koken is not the only Japanese tool company that rivals Snap On in terms of tool quality. Saws, chisels, electronic tools, pliers .... In the usual Japanese pattern, they would have a specialty manufacturers (wrenches or pliers say) that make whatever in their focus area VERY well, and regard doing it well as more important than year-to-year profit. Japanese consumers also tend to be very picky, so companies see consistent quality production as essential to their long-term survival -- not just honor and bragging rights (though I doubt they would declare themselves the best as we would in the USA). After WW2 Japan was low quality for a while since they were nearly destroyed. But as they recovered into the 70s their cultural tendencies took over and quality jumped since they could afford to do better from that time forward. Today, globalization hurts that somewhat but the impact has been slower in Japan since the people are very picky so they will spend more rather than just buy the cheapest junk. Homes being small may enhance that if nothing more than having less room to put things.
Japanese food is also super high quality at relatively low price points.