In most real-world use of the term, a paradox isn't something that's impossible, it's just something that intuitively seems wrong when you first think about it.

"I got a Prius so now I am spending more money on gas" sounds ridiculous, but it would be an instance of this paradox.

One of the classic examples is highway traffic. You want to prevent traffic jams, so you increase the number of lanes. However, now that there are more lanes, people see less “cost” in driving, leading to even more people driving (e.g. to go on more day trips or as alternative to public transport). This can cause the traffic jams to become even worse.

So, increased efficiency can sometimes not lead to reduced latency, which goes against our natural thinking.

It’s surprising (not using the term paradox) in situations where demand was seen as inelastic.

An example of probably inelastic demand is the cost of diamonds which has fallen as synthetic diamonds enter the market. But people typically don’t buy more engagement rings than before.

With code it could be different. People might think that the amount of code that needs to be written is fixed, so the ability for a person to write code implies a reduced demand for people who write it.

In reality, bringing the cost down may unlock new use cases, so the number of actual coders might increase.

Jevons paradox starts with some resource being used more efficiently.

A classic example could be coal. The first steam engines used a ton of coal, but over time more efficient steam engines where created that used way less coal.

One might think that this caused the global coal usage to go down. But the opposite happened, as the overall cost of doing something with a steam engine went down.

Note, that the price of coal itself can remain fixed in this example. So Jevons principle is not (directly) about a resource changing in value.

If LLMs make codes cheaper to produce, then obviously more code will be produced. That's not an instance of Jevons paradox even though the article claims so.

You could say that LLMs means that we can create software with less of the resource that is human software engineers. So one might think that we'll need less software engineers in the future. If, on the other hand, we end up needing more software engineers, then that'll be an instance of Jevons paradox. But the article is not making that claim.

The paradox is usually presented as:

The People: Hey local government! The roads are so packed with cars they are useless. Fix it!

The Government: We hear you and just finished a huge road expansion project. The roads now have 2x the capacity! Enjoy the new fast roads!

The People: The roads are just as slow as before because they are packed with 2X as many cars now!

So, the paradox is that greatly increasing the capacity of the roads led to the roads being just as slow as before. Maybe even slower. This is because there previously were lots of potential uses of the roads that people did not enact because it would not have been worth the hassle. But, now with 2X the capacity, those uses become viable. So, more people find more uses of the roads up until it gets right back to the limit of everyone patience.

Apply this to coding and you can predict: Coding is much faster and easier now. So, why are all my coders still so busy?

Yes. Jevon's paradox is that if we need less X to do a single Y, we end up using more X doing Y.

Anyway, it's an specific observation about a single X, Y pair. It some times happens with other things, but anybody claiming it's a universal rule don't know what they are talking about.

Unit cost is down but aggregate cost is up.

Yes, I believe you are correct (but imprecise which is why the other commenter disagreed with you).

We pay less per unit, but we pay more in total.

No, we pay less for it. But there's much higher demand so overall use goes up.