Wooo, sorry to drop in late!
If there's one thing I've noticed since moving to Japan, it's that everything is so damn hard to find. I only just found out after 18 months of living here that there's a great audiophile store on the fourth floor of a totally nondescript building in Osaka's electric town!
From what I remember of prices back home in Australia, there isn't much you'll get a good deal on. Japanese consumers are total suckers, they'll pay whatever inflated prices the shops set their wares at. I usually order off amazon or ebay, I've never actually bought any audio gear in japan because their prices are too high.
I can't speak much for equipment prices, although Audio Technica is definitely cheaper here than back home. However, vinyl here is generally great quality and quite cheap for old-pressing imports, make sure to check out some of those back-street record shops! They have some real gems.
Oh, and no trip to Japan is complete without a trip to a Maid Cafe (and/or a Love Hotel)!