Maybe a better question is how do the caucasian shops do it... How could they survive as profitable businesses when the prices that they charge are so out of touch with reality? In the current economic climate, what perc of the population can afford their prices?

Or maybe they aren't surviving, lol...

But about Ginza. I think it's a combination of a few things, but owning the properties that they operate out of could be the biggest factor, especially when they were bought a long time ago when property prices weren't so crazy yet.
This gives them a lot of freedom to set competitive prices because they have much lower overheads.