First surprise were youth hostels. For a single person staying in a dormitory they are not really cheap, but still affordable. For 2 people in a double room it is way too expensive. We had to stay in a youth hostel on our first night in Japan because everything else was fully booked and it was the most expensive accomodation we had in all Japan. There are some private hostels as well that are a little bit cheaper, but they only exist in the very touristy destinations.
But we also wanted to try something very Japanese and opted for a temple stay once. Big mistake. Everybody has heard of paper thin walls, haven't you? Unfortunately, here they exist literally. The sliding doors are just made out of paper - nothing else. And although the temple hostel was actually quite quiet, we could hear our neighbours whispering. So much for privacy. The same applies for ryokan, so called Japanes guest houses. Very nice to look at, but no sound proofing whatsoever.