I don't think I ever read of any nation of Kulthea diverging from the typical model of: An Upper-Class being a small percentage of the population & a Lower-Class being the vast majority of the population, with some Merchant/Middle-Class sprinkled in there.
In our own world the middle class makes up almost half of today’s society, but in a feudal society more than 90% of the people were peasants. That would mean the middle class was a much smaller percentage of the population than it is today. It’s also interesting to note that in renaissance society the middle class was below the merchant class. You had four classes: peasants, middle class, a merchant class who were rich, and nobles - who were sometimes poor.
But what of those lower-class people who have magic? Well, think of it this way: today we have different levels of access to tools of learning. If you are exceptionally wealthy you can go to one of the 'big' schools like Harvard, Cambridge, MIT, etc... which an employer would consider above the college they had to look up in order to know where it was. Not only that, the connections being at that level would entail. The same goes for a magic world. The upper-class would have greater access to more capable instructors, and they very likely don't have anything close to resembling scholarships.
One of the prices listed on the link I posted was the cost of a year at Oxford @ £8.5, which was well out of reach of almost every profession listed.
One of my favorite ShadowWorld supplements from old ICE was the one with the magical college on the hidden isle. That’s a place where magic likely would be much more commonplace. No idea if Terry considers that one canon.
Sel-Kai has schools that teach magic, so it’s definitely something that is present in the city. I think there is a comment in one of the books that many have magical aptitude, but have never received training. Certainly, that idea is presented in Loremaster Legacy.
I just don't think it is in anyway accurate to assume that the commoner would be wealthy just because the upper-class is exceedingly wealthy. In fact, I would argue that it would be the opposite because at any given moment all resources are finite - even the imaginary / made-up ones like money - so if some have so much, then others will have very little.
The information I found was mostly on the 1300s. The Renaissance period that Sel-Kai is supposed to be based on would probably have somewhat higher income, but I am still pretty sure the average person back then never laid eyes on a gold coin in their life, and the peasant class would still have made up 80 – 85% of society.
It’s also worth noting that while some shopkeepers came from the lower class, most of them came from wealth. Regardless of skill, it took wealth to start a business. In Paris shopkeepers lived over their shops, and interestingly the nobles lived on the ground floor of their buildings. With no elevators to carry you up five floors a person’s social status was measured in part by not having to climb stairs. The lowest servants lived on the top floor, and today those servants’ quarters sell for millions in districts like the Latin Quarter or the area in and around St Germain.
As for the herb gathering, in a world where it is likely 100x more dangerous to go out into the wild than it is on our world (or more, I would believe), very few would be able to do this.
Xaar has a good example of this,
A tree that produces an herb that gives lifegiving, blooms once a year, and is guarded by a powerful demon; even assuming you could make it to the location of the plant past all the other challenges. Getting this one herb could easily be the center of a campaign that gave you months of gameplay.
This has been a bone of contention with me. I think the setting is high magic, but so many argue that it is not, that the average person on Kulthea sees magic maybe once or twice in their lifetime. I think that is more like per week.
This is really up to the GM & Players imo. I see ShadowWorld as high magic in the sense that it is more like Faerûn than it is Middle Earth. I don’t see ShadowWorld's magic as being commonplace like it is in the Wizarding World of Harry Potter, with modern conveniences being replaced by magic, and usually for the better. The amount of magic you see in Kulthea each week is likely to be based on your role in society. The average farmer would probably never see magic at any point in their life, but a Loremaster could see it daily. An ordinary person living in a city might see it every so often, but it would be a noteworthy event.
I also tend towards Dragons being legends that no common folk believe still exist, and the civilization of the K’ta’viir being so far lost in the past that only a select few like the Loremasters or the Jerak Ahrenreth know they were a real thing 100,000+ years ago. It’s not that the players will never encounter these realities, but in my mind 1st level PCs aren’t wise to the secrets of the world and must grow into that knowledge.
That’s just me though. If the game you want to run has common magic, and legendary beings are more commonplace, then go for it. I don’t think there is only one right way to run an RPG, or a setting, and I really disagree with the sentiment of "no you have to do it this way because "creators intent!" I’m also of the opinion that if someone wants to run a high-level game there is no reason they shouldn’t do so as long as you are committed to doing it well for the sake of the players.
I do think Kulthea has three major limitations on the free exercise of magical power.
Flowstorms can be triggered by runaway magic, which makes problematic to cast high level spells.
Groups like the Jerak Ahrenreth seek to kill or subvert powerful spellcasters. If you have power you probably don’t display it openly. By the time you have that sort of power you likely know about these sorts of groups.
Portals to the ash lairs or the pales can open randomly, and magic running wild can sometimes serve as a catalyst. Having a demon from beyond the Pale demon step though a portal into your living room at dinner time is usually a downer; especially if he then tries to sell you aluminum siding.
