This resonates with me pretty well, even though I don't have such long experience. However, my wife has a small website selling vintage items to Japanese custom

This resonates with me pretty well, even though I don't have such long experience. However, my wife has a small website selling vintage items to Japanese customers, so we have some experience with online advertising over the last couple of years. Apparently, Google isn't as strong in Japan as Yahoo. At least for the demography that reaches my wife's website over the last couple of years. We see this quite clearly on (organic) site visits. Given this, I would assume that advertising on Google would be cheaper than Yahoo Ads in Japan. However, it's not the case. Google adwords are far more expensive and deliver far worse results for the same campaigns. Maybe competition in this niche is not well informed/stupid and uses Adwords more than Yahoo, which drives the price up, but to me it doesn't make sense. If Yahoo gives better bang for the buck (and it does!), then advertisers would naturally shift there, which would raise the Yahoo price, and reduce Google's. However, that does not seem to be the case. It feels like Google is somehow inflating the prices not completely in line with supply/demand.