Magic is a constant force in the world, but it isn’t everywhere. There are no guarantees that any given town will have some sort of arcane practitioner in residence; it’s a rare village that has a genuine hedge wizard and not just a general practitioner of alchemy and odd little cures. In the same fashion, most members of a given priesthood have no access to divine power. The empowered priests, templars and the like are a significant minority. Even arcane organizations such as wizard’s guilds may have a large proportion of “mundane practitioners” in their ranks.
Most people must get by with non-sorcerous uses of the magical properties of a world: war-alchemy purchased when one can’t get a warmage, fountains enchanted a thousand years past that still water an otherwise mundane village, and so on. And the world itself is lightly magical, infused with the stuff. It took no mad wizard to create an owlbear — that’s just a creation of the world itself.
The major sources of magic are arcane (which itself divided into “high” and “deep,” also known as “star magic” and “world magic”), divine, elemental, spiritual (or “primal,” drawn from the Overworld) and spectral (or “shadow,” drawn from the Underworld). Magic granted by pacting with outsiders is usually arcane, though it may be divine in the case of angels or devils. Unfortunately, these variable sources make magic ridiculously hard to classify. Sages and wizards frequently bicker over the “latest theories” in much the same way that biologists argue back and forth for the proper taxonomy for a singular creature. Most casters simply have to be taken at their word: if a fire-mage says he practices high elementalism rather than world magic, direct grafting of elemental power or an infernal pact, it takes a singular scholar to prove otherwise. While “wizard” and “sorcerer” and “warlock” may have specific meaning in game mechanics, they don’t in the world. “Wizard” is favored by those who want to seem wise, “witch” or “warlock” implies a certain deceptive or sinister mentality, “sorcerer” speaks of having power but no particular implications about how it’s used, and so on.
Enchanted items themselves? They’re around, to be sure; it’s an old world, and these things frequently have no expiration date. Mechanically speaking, a +1 item is probably not magical at all, but a mastercrafted piece of work. Many magical weapons and armor are not created by proper spellcasters, but forged by those with the knowledge of inherently magical metals, quenching processes, or elemental forges. And of course there are the wizards and sorcerers and the like. Each item does (and should!) have a story, be it commissioned for a nobleman, forged by giants as a blood debt, or granted by an enamored djinn.
There aren’t magic shoppes, even in the largest cities, that have genuinely powerful items on sale for coin. Magic items have their own economy, separate from the cash economy. Most magic items are exchanged for other magic items, as it’s difficult to put a price on the things. Usually the best place to go for such an exchange is an arcane organization, a government, or a temple — organizations large enough to accumulate a variety of such items, and with the resources to hold onto them. Temples are particularly favored, given that they tend to be willing to offer very reasonable deals for the right trade. A hulking warrior can’t get much use out of robes of spun moonlight, but the temple of Shessa certainly would. And they might have an impressive firebrass battleaxe in their vaults kept against the occasion of just such an opportunity.