Just came back from Kawaguichiko and stay at this ryokan. I booked just a day after the Golden Week ended, and what a difference it made (46,000 -> 23,000 yen!) The price may still be hefty, but get this: It includes a 7-course sukiyaki (or shabu shabu if u prefer that) dinner and a sumptuous breakfast for 2! Especially the sukiyaki, between me and my gf, we couldn't finish all 4 plates of fresh beef. And we left a lot of sashimi and sushi behind :(.
The room is tatami style, spacious and can sleep 4 persons! It has a beautiful Kawaguichi Lake View (but not Mt Fuji as its at the back). There is free wifi internet at the lobby (but not in room), and free shuttle bus service to the Kawaguchiko Station (although its only a 5 mins walk). By the way, the rooftop onsen (hot spring) is open 24 HOURS !!
The ryokan is also a 5 min walk to 2 great attractions, the boat ride and ropeway. Get a package ticket for 1,200 yen! Absolutely worth it; if you can't climb the Mt Fuji, at least see it in a leisurely way.