When I imagine Low Fantasy, there's usually a House/Guild/Company that has one special person who bolsters their trade. Whether that special person has a magical affinity to trade, fight, vex, spy, or charm... even a single magical advantage, when applied consistently, could lead to market dominance.

For example:

• A successful and renowned caravan company has a magic-attuned fighter who can fend off thieves and ambushers, even if that means being the last alive.
• Local herbalist is suspiciously beating all of the competition. Upon further investigation, it turns out they hired a magic-attuned individual to charm their goods, evoking positive affect in customers.

You should implicitly define an upper boundary to how many people can have magic abilities, and to how often said people have powerful abilities. For example, say the nation that your story exists in has 100 million people, and each 100 million yields a handful of magical people. One special person is probably a baby, and two of them are probably quite old. A couple magical people might be quite powerful, another couple has quite mundane abilities, and perhaps one is somewhere in the middle. There may be more or less than a handful of magical people in the nation, since people may come to or leave from your nation.