BTC --> MtGox JPY = 2.5% + your trading fee, let's say that's 0.3% = 2.8%

Mtgox JPY -> JPY = 0 I think (or some flat fee, which is negligible if you're doing large enough chunks at a time)

JPY --> USD = .1% or less unless your bank gouges you, plus another flat wire fee

USD --> Bitstamp USD = 0.2% (again for high-volume account)

total = approx 3.1% to 3.4%

That leaves a solid 6 percent profit on the table. If anyone who has a Japanese bank account would like to team up to make this happen, let me know. I have bots which can do the trades efficiently and high volume  mtgox and bitstamp accounts (= lowest fee tiers). I also have access to enough capital to make it worth while. Only thing I don't have is a Japanese bank account in the hands of someone I trust. Or do it yourself, I will applaud you and help in any way I can. I agree with joesmoe2012, this needs to be done for the good of the whole system.