On top of what Michael said, there is only to add that this myth that Ryokans must be expensive comes from the issue that Ryokans are normally not as space-effective as modern hotels - and therefore more expensive when it comes to downtown locations.
The maintenance costs for wooden build type of the room, the tatamis and the family-style"live in your own home" style service level is not manageable for a 300-room sized Ryokan - next to the fact that a 15-floor building is not really what you would call traditional Japanese architecture. But if you want to pay the real estate costs (i.e. inheritance tax on property, etc) for a downtown location such as the famous Tawaraya inn in the middle of Kyoto, you will have a certain pressure to either be expensive or convert into a western style hotel where you have a much higher sqm-efficiency to justify the investment. The cheaper ones left in Tokyo can most probably survive because they are so rare and therefore ARE popular with tourists, have a tourist attractionhigh occupancy and are able to pay their bills.
Therefore, cheaper ryokans can be much more found in country-side locations and generally not so crowded places than downtown Tokyo or in the heart of a tourist destination. They can still offer the environment, but do not have the pressure to make room for a 70-floor high office tower.