On the one hand, a spire appears to be a single large city state, but in fact it quite effectively split up into habbles. Consider the fact that if you want to move stuff (grain/raw materials/finished products) even one habble up or down, you need to use one of four ramps/stairs to climb or go down 50 feet. These are real bottlenecks and I think have a number of repercussions.
1) There's no evidence of beasts of burden, so all transportation must be done by hand. In addition, I don't think we have seen people using carts/wagons to move stuff around. This kinda makes sense, because if you want bulk goods from a different level, I don't see how you get a cart up the equivalent of five flights of stairs.
2) Traffic on the stairs/ramps is going to be a mess. Anyone who has business on a different level has to go through here. Add to this the fact that there are tool booths to go through (for collecting fees) and things get worse.
3) It would make sense if one of the staircases was blasted away and an elevator put in place. They do have lift crystals after all.
4) There is a distinct advantage to being on a higher habble. After all, it's easier to move commodities down a ramp than up it. Think about rollerblading down a 2 mile ramp...
5) Note also that these bottlenecks make for great warfare targets. After all, if you want to contain a rebellion, all you need potentially need to do is hold the staircases. Heck, if you're on the upper habble, you can destroy the staircases. Needing to climb 50 feet straight up to invade is going to be hard.
6) We also know that there are extensive ducts/vents going between the various levels (for critter and Auroran marine use). Given the tariffs and the traffic, I think it would make sense that there is a lot of smuggling going on through these back routes, and some of the bigger ducts might even be official secondary paths between the habbles.
7) In any case, all this means that in essence, each habble is going to need to be pretty self sufficient. This is partially shown by the fact that the most important habble (Morning) "wastes" space for meat vats. In any real city, this type of industry would have been moved to areas with cheaper real estate. Of course, it might be that they don't have the technological knowhow to move the vats anymore.
This self sufficiency comes at the price of efficiency. If every habble needs to be able to support itself, then you can't have the highly urbanized "city centers" that get supported by the surrounding countyside. In ancient Rome, the center of the city had a population density of ~70,000 people per square mile, but had to import grain and commodities from farms and villages throughout the empire. In contrast, it took about 1 square mile of cultivated farmland (including grain, mill, vinyard, etc.) to support 500 people.
9) Now granted, the spire has "water gardens" and vats for food, (so enhanced production) but I still think this pretty much means an upper limit of ~5000 people per habble. This includes nobility, farmers, technicians, store owners, etc. Specially important habbles might be able to push this a bit higher at the expense of the neighboring habbles, but I would guess that 10,000 is a hard limit.
10) This makes one wonder why more habbles didn't go the route of Landing and make their own holes in the wall. Obviously there are diminishing returns for every extra hole, but think of a habble midway between Landing and Morning. Bringing goods to this habble from the outside requires transport 2500 feet vertically. That means that (e.g.) every beam of wood on this habble required a human to carry it down (probably - up would be crazy) a distance of the tallest building in the world. It would be real expensive.