I haven´t purchased from Japan yet, but especially Ishibashi-music seems to have a great reputation.
Their actual price is 176.000 YEN for the RG8670. Assuming that you live in the United States, you´d have to add 14.000 YEN for shipping and insurance. So, a total of 190.000 YEN which are 1750,- US Dollars right now. AND: you also might have to pay taxes or customs. As far as I know, Americans are supposed to pay those taxes, but my impression is that not many people actually get charged. But I can´t tell you for sure (I guess noone really can!).
I´ve also wanted to buy a guitar from Japan and my impression was that there is no to a very little difference in price. I am quite sure that Ishi and Ikebe will have almost exactly the same price.
Koichi offers special prices for students, but no other offers are made as far as I know, so the price I mentioned is quite sure what you´d have to calculate with.
Oh, and as I wanted to order a RG8527, Koichi told me that they will only order J-Customs upon reguest and building the guitar will take 3 months! Some weeks ago, another Jemsite member said that he even had to wait almost 6 months for his RG8527! Too long in my opinion; remember, you have to pay beforehand!
I hope I could help you a little