http://www.nouhibus.co.jp/english/shirakawago_kanazawa....According to the above, the one-way bus fare is 4200 yen, 1800 from Kanazawa to Shirakawa-go, 2400 from Shirakawa-go to Takayawa.
In the Shirakawa-go bus terminal, there is a tourist information centre. You can leave your luggage there for a fee. I don't know the cost, we did a day-trip there from Takayama.