Assuming a prevalence of magic and a large number of magic sweatshops, for lack of a better word. What non-combat items would be mass produced first in a pseudo-medieval setting?
It will probably be magic that helps with everyday problems and needs:
Healing supplies. Got a cold? Take this pill, gone. Food poisoning? This potion cures it. So many uncomfortable conditions that magic can heal at an instant. Also, things like massage spells would probably sell well. And anti-pregnancy magic. Oh, and not to forget that you don't have antibiotics, so magic can be the only rescue for SO MANY lethal medieval sicknesses.
Cleaning spells. No more doing the dishes, cleaning your cart, doing the laundry. Also, getting rid of lice and fleas...
Teleportation and flying spells (for superfast travel)
Entertainment: trinkets that give vivid and exotic dreams, illusion spells, shapeshifting potions, these kind of things... also, to be honest, sexual entertainment would probably be a thing. I mean, there already are massage and illusion spells... right?
Communication: long-distance communication can only be done via magic, so it would definately be a thing.
Illumination: candles were super expensive, so after dark, there wasn't much to be done. Magic lamps might be a big game changer, here.
Anti-Smell Charms: Considering the situation in big cities, especially in waste and feces disposal, i think anti-smell charms are going to be a best seller...
As a rule of thumb: Whatever you can imagine that would make peoples lifes easier, is fun or can be misused in a sexual way, someone might produce and sell.
If the setting is that magic users are common and abused, why not put them to work maintaining the city shields against an overwhelming enemy? In this situation, magical items would actually be disdained and magic users considered lower-class citizens (the poor working class).
If you want a product then, it could be related to the survival of the city... such as porting in water or genetically-magicified food, and clothing. (Again because of class society, only the lower class eat this food, while the REAL food is reserved for the upper classes and warriors.)