Does it make sense to consider the primary purpose of housing to be a gil sink/anti-RMT tool? Even if we say that there are three, four, or five times as many players as there are available plots, that also doesn't mean every player is looking for a house either. Instead of drastically increasing the cost-to-entry, doesn't it just make more sense to increase the number of wards, and add new housing locations? When Ishgard is made available, for example, it will presumably come with the same number of wards as all current districts. Beyond that, the only other ways I can see to increase availability would be to either breakup congested servers or force people who own multiple houses to give them up somehow. A gil increase only prevents new players from entering the system, it doesn't do anything to actually make new space.