When a world has magic how do the blacksmiths keep their doors open?
After all, the mage in her tower can make in an afternoon what takes a blacksmith a month. And they don't have to deal with unbearable heat or shoulders worn through by twenty thousand hammer-blows.
Even if the mage charges many times more per hour than what the smith does, her sheer productivity will drive prices into the ground. And sure, there's an obvious counter argument. Would a mage really spend their time stamping out horseshoes? In all honesty, it's certainly possible. Mages would have all kinds of dispositions and interests. No doubt some would enjoy working with metal. Others would like the steady income.
But even if we say that no mage would ever stoop to metal work, nothing changes. The mage doesn't have to be in direct competition with the smith to undermine the smith's income. All they have to do is build a machine that competes.
A mage who builds a magical forge has just created a means of production. She can walk away to more 'suitable' work and the magical forge will still undermine the smith each day it continues to produce. It doesn't matter how rare or expensive magic is or what work mages are inclined to do. They'll produce mechanisms that produce. And the smith, the tailor, the carpenter would be forced out of business.
Magical Revolutions
We know this is true from our own world. It's how the industrial revolution transformed our society. Magic is often depicted as far more versatile. So why do so few fantasy worlds deal with the consequences of that logic?
Treated seriously, magic isn't just pretty. It's a way of building productive capacity. It does not sleep, tire, unionise, or age out. It does not suffer from bad backs or cataract. It does not stop to mourn its mother or feed its children. There is no contract to negotiate, or wage to pay. The only real restriction on production is who controls the magic that can create the machines. Whoever controls that controls the economy.
What Magic Touches
Let's start with crafts. The golem in the workshop labours without rest, takes no wages, and produces the chair, dress, or shoe for whatever it costs to keep the golem running.
It reaches food, too. A magical grain that grows in weeks instead of months, an irrigation system that never fails, a herd magically bred to grow twice as fast: any of these undercuts farmers who don't have access to them. None of them need a mage in attendance once it gets going. Most fantasy treats agriculture as untouched by magic. Perhaps because the peasant in the field is such an iconic image of the genre. But if you're honest about how the mechanism works, the peasant would have to find a new job.
Then health. A potion that mends a broken arm in an afternoon eliminates the village apothecary. A healing rite that closes infection undermines the surgeon, the midwife, and the herb-gatherer.
It climbs into thought. An elixir that sharpens recall, a charm that holds a name in mind, a binding that lets a scholar work for sixteen hours without fatigue: these repeat a by now familiar refrain. Don't have access to them? Then you don't have a business.
It extends longevity. Magical methods of extending lifespans mean expertise sticks around and new generations must wait even longer for their inheritance. This not only stultifies society, but also tilts the field against the people who can't access such concoctions.
It takes motion. A portal, a courier-spell, or a flying carpet compete directly with the caravan-master, the messenger, the dock-hand who loads the slow boats. Magic doesn't have to make something to gut an industry. It only has to do the work the industry was being paid for more cheaply or effectively.
Taxes and Policies
Perhaps taxes or policy can stop this? You raise the price of magic, you ban the workshop, you protect the trade, and the smiths return to their squares.
But this runs into the same problem as other attempts to slow more effective means of production. The places that do so fall behind those that don't.
This is what happened during the industrial revolution. Austria entered it as one of Europe's great powers and Britain's equal. But the Habsburgs, who were Austria's rulers, distrusted the new machines. The emperor feared the railway would carry in revolution. So Austria dragged its feet while Britain steamed ahead. A century later Britain ruled the largest empire the world had seen, and Austria became a second-tier power.
Magic would function similarly. And unless everybody collectively decides not to allow magic into the economy, whoever lets it in pulls ahead and comes to dominate their neighbours.
A Slow Decay
If magic is allowed to transform the economy another thing starts to happen. Once the smiths no longer earn a living, they also don't take on apprentices. Today the 'for sale' sign goes up in our village, while the forge in the next one already closed a decade ago. The tools themselves stop being made because the toolmakers also lost their job. The good iron is no longer mined the same way. The alloy recipes are no longer written down.
After one generation the knowledge begins to fade. After two it is gone. The trade isn't just unprofitable, it's beyond recovery. A government that decided, a century from now, to bring back the smiths would struggle immensely. They could fund it, they could legislate it, they could offer a bounty for any student who took up the hammer, and they would find that the practice would have to be relearned in its entirety.
A Closed Class
The comparison to the industrial revolution breaks in one place. In our own world, a loom is just a machine. It is theoretically possible for anybody to buy one, run it, or copy it. Ownership spreads, competitors multiply, and people who started out with no machines can end up making a fortune.
That's not possible in a world where the means of production is magical. There the device can't be copied by those who are being ruined. Every device gets built by the same class of person.
If the devices need regular magical maintenance it gets worse. A non-mage can't copy it and can't even run it without paying the magical class for the privilege.
Mages will compete with each other, of course. They'll undercut each other's prices, poach each other's patrons, and do what people do. But that decides which mages win, never whether mages win. You end up with something that's not quite a monopoly but shuts out a huge chunk of the population nonetheless. No sum buys your family in. You're born with the talent, or you're born outside the economy.
Whether the mages rule in their own name, serve a crown, or answer to a guild that owns their contracts depends on the world you're building. Whoever sits at the top, the same people are on the outside.
The Social Effects
Kingdoms will struggle to remain picturesque when this many people lose their trades.
The smith who cannot compete, the farmer whose harvest is undersold, the healer outcompeted by the potion, the apprentice with no master left to teach him: these people don't disappear. They accumulate. They have children who grow up in houses where the work that once defined the family is now only something a grandmother half-remembers.
The resentment compounds because the conditions that produce it are structural and do not ease. And because the trades themselves are gone (and not coming back), the resentment has nowhere to direct itself except at the system that took them. There is no hope of becoming a mage if you don't have the gift. There is no hope of opting out, because the magical economy has reached into every nook. The pressure has nowhere to go.
A society that produces this resentment has two options. It can build mechanisms to absorb the pressure: representation, controlled dissent, rituals and institutions that give the disadvantaged somewhere for their anger to go. Or it can decline to build those mechanisms and live with the consequences.
The pressure will always find a release. The question is only who, if anybody, shapes it.
If your setting has magic running through every aspect of production, and a ruling class that benefits from it, and a peasant class that seems content in the sunshine, then you have not built a world. You have built a postcard.