As the best of my knowledge, the ranking was decided by the dev in the initial design for each housing area. Some of it does not makes sense at all, but it is subjectively affected by proximity to services, panorama, etc.

Ex: my house is on Lavender, 26, and besides beign relatively close to the MB, there's not an even remotely nice view. Still it set as first class.

For ref ther's the priceshart as of 3.3 (unchanged yet)

https://www.reddit.com/r/ffxiv/comme..._updated_with/