Do you have any experience teaching Japanese students? I have. More than 8 years' worth, from high school to university to adults. Trust me, you don't know what you're talking about.Everywhere you hear stuff about how bad Japanese people are with learning English and about all the spelling mistakes they make, etc. Personally I don't think they can be that bad at learning it,
By looking at pricing for English books on Amazon Japan, I think it is about twice as much as pricing in USA. Is it mostly due to the shipping cost? Many book retailers in Japan use the airfreight service from USA to Japan and books are very dense and heavy. So, the shipping cost is not that cheap even though those companies get the very good airfreight rates from the shipping company.