from my experience in buying knives @ Kappabashi, tokyo, I can say that it is not easy for an in-experienced person (not local to the area / no enough knife knowledge) to find a good deal. Mainly because it is rather a "cutlery market" rather than pure "knife market" and you maybe struggle to find decent stuff as there are many cheap , low quality things around as well, not to mention there are lots of things other than knives.
also, the retail price isn't necessarily better compare to some of the japanese online retailers. if you speak fluent japanese and know what is the right price, you maybe able to bargain a bit, but it didn't apply to me.
I use to spend a day there trying to find some "nice knife @ good price" but failed. I did bought a little cast iron teapot