I have visited Japan several times a year for the last 20 years, working for a Japanese company, and have been to 7 other Onsens previously, ranging from basic to elegant, so do have a good frame of reference.
I admittedly have high expectations, as I felt justified for $800/night, and was somewhat surprised when I arrived. Rather than the beautiful, tranquil, and zen atmosphere I was hoping for, the atmosphere was just dated and seedy. There was no area to relax, other than our room (where they served our dinner), or a "relaxation room" which was an empty room, with 2 coin operated massage chairs. The lobby was a room with several more coin operated massage chairs, and a long table with benches, like a picnic table.
The food was plentiful, and the service was good and friendly, but rather than the delicate and beautiful food I have received at other Onsens in this price range, a couple of the courses were good and fresh, such as the fish and tempura, but the rest seemed to have been cold leftovers from the fridge.
The baths and locker rooms had more the feel of an old run-down dormitory than the beautiful, traditional Japanese experience I had hoped for based on other Onsens I had visited.
To sum it up, knowing their NO Refund policy, my family and I unanimously opted to throw away the money, and leave early the morning after our first night (we booked 2 nights), as we felt it was better than wasting a precious day of our 10 day vacation.
No regrets.