Spellcasters of each level
As per Settlements in the Game Mastery Guide:
A settlement's population is left to the GM to assign
The guide describes the highest spellcasting level available for hire in each size class of settlement, and what category of magic items are available for purchase. However, it says nothing about the total number of spellcasters, their classes, their prevalence per total population, or even how many of each settlement exist within Golarion.
If we're willing to consider outside sources, D&D 3.5 is much more clear on these questions. Pathfinder drew largely from D&D 3.5 as its basis, but was unable to copy its settlement rules directly since those aren't part of the SRD.
In that regard, the D20 Demographics Calculator is useful, providing a complete breakdown of spellcasters per class and level, as well as the number of settlements in a kingdom of a given population.
However, according to an answer on this related question, Pathfinder's vague figures on population by class is an intentional design choice. This makes it unlikely that any future book will nail down canon numbers for exactly how many wizards, clerics, etc live in Golarion, leaving it up to individual GMs.
A reddit thread also makes some estimates on Golarion's population.
Magic items
The demographics rules are irrelevant for who can own a magic item, since anyone with money can simply travel to a major city to buy their item.
Bear in mind that NPCs don't have to follow the wealth scale that player characters do. A merchant of fifth level might be a millionaire. Wealth and power go hand in hand; Golarion is still essentially mediaeval, not some futuristic utopia, so those in political power are more able to afford magic items.
Magic swords
We can assume that most people cannot afford a magic sword, given the typical wage and living expenses. A trained hireling (3 sp/day) would have to save his entire wage for twenty years to afford a single magic sword (2,000 gp).
The only people who can actually afford magic items are either rich (e.g. the best doctors, earning 10 gp/day, could plausibly buy one +1 sword in a year) or very powerful (royalty, nobility, and their most important servants). Most soldiers would not be outfitted with such equipment, and certainly not most peasants.
Buying such a low-level item in a massive city would be trivial, but having the money to do so would be extremely rare. Magic item owners are the 1%.
Social bonus items
The pricing guidelines suggest that a social skill enhancing item costs the skill squared times 100 gp. By the time we get a significant +5 bonus (enough to turn an untrained guy into an expert), we're into the same price bracket as the magic sword.
Even a single three-minute potion of eagle's splendor costs 300 gp. That's about a year's salary for a doctor or someone with a similar high-paying job.
You need to be someone very important like a major diplomat to wear an item that improves your social skills.
Teleportation and mind-affecting
The spell forbiddance (Clr6) will permanently block teleportation into an area of 240 ft. by 180 ft. by 60ft tall, for a little over 20,000 gp. You can hire someone to do it in any major city, but the expensive material cost is more than even the most highly paid salaried worker makes in five years.
Teleport blocking is only available to extremely powerful factions and very few individuals. It's practically a nation-state capability.
Teleportation itself is more affordable, a 5th level wizard spell costing 450 gp for three passengers on a one-way trip, or 150 gp each. This is still a luxury beyond most people, and especially expensive at any kind of scale (e.g. teleporting an army). Nearly everyone will travel the old-fashioned way. However, a rich doctor or lawyer can take his family on a holiday once every few years.
Immunity to mind-affecting is difficult (mind blank is an 8th level spell costing 1,200 gp per day and still doesn't grant total immunity), and mind affects are as cheap and common as a first level charm person or second level detect thoughts. Immunity to mind-reading or control is extremely rare, to the point that only a tiny handful of people in the world have access to it.
Prying into someone's mind is likely to be illegal wherever you go, although no doubt some criminal mage spies could be hired for a fee (60 gp for a detect thoughts spell, maybe 100 gp all-inclusive). It's something only available to unscrupulous nobility, perhaps investigators working on the most high-profile cases, and the top 1% of society.
Conclusion
Almost nobody in Golarion has magic items. The rulers of society have access to nearly any item or spell they want. The top 1% of society has access to a few minor magic items, maybe, and it's going to be a major purchasing decision.
