It's worth noting that the "generic" got pulled, but there have subsequently been several attempts to bring competitive products to the market to compete with api-pens. It's not like they have a natural monopoly. The thing that is keeping competition out of the market is the FDA. This is a product that is not exactly at the cutting edge of science so either all the competition is really incompetent (I find that doubtful) or the FDA is basically creating an artificial monopoly by keeping competition out.

In my opinion, most cases where you see one company able to charge outsized prices for their products, if you scratch the surface you'll find a government created monopoly, or near monopoly (wireless spectrum is an example of this) or regulation created situation that protects one company from competition.

At the very least you will not find a free market. Because in a free market, people will compete if anyone gives them even a small pricing umbrella. Even for things that require very highly refined manufacturing techniques, like drugs and electronics. Look at the cellphone market, nothing is more precisely built than a smart phone yet we have huge numbers of them in a wide variety at low cost, because the market is mostly unregulated.