With the Euro being rather strong, I'm pretty sure (without checking) you can get it cheaper in Japan.
And if you go to big places like Yodobashi you usually will find someone who speaks (some sort of) English. There's also the chance of getting a point card and save even more (in the example above, both Yodobashi and Sofmap would give you 10% of what you pay for that Nikon - That's like an extra battery and some small things for free). But some places will ask for your alien registration (happend to me at SofMap but it seems to depend on the guy there because a friend had no problems). They will also most likely reject you if you live in a hotel.
You could still try to get one, buy the camera, get the points, come back the next day (Many places will not let you use the points the same day you earned them), get some accessories and then make a run for it before they had a chance to check it.
Depending on what you're looking for, smaller shops really have a hard time beating the prices of the bigger ones.
It helps if you speak Japanese. Do you?
There's also some shops in, for example, Akihabara that sell duty free stuff. But I have no experience with them.
If you want to travel in Japan a lot, you might want to check out the Japan Rail Pass.
And if you don't want to use it, be advised that on some routes, going by train isn't actually cheaper. You can fly from Tokyo, Haneda to Shin-Chitose (near Sapporo) for around the same amount you'll pay for a rail ticket (including Shinkansen). The plane will take about 2 hours (including boarding and such) while the train takes 15+ hours. You can have it cheaper by not taking the Shinkansen but that'll take even longer. If your time is limited you might not want to do that.