Pricing controls probably aren't even necessary. Did you know that government programs like medicare aren't even allowed to negotiate for lower drug prices? If they could, it would put a major downward pressure on drug prices (which is why they're not allowed to do this). Countries with socialized medicine have this built into their medical systems. Something like the NHS would not only not accept this kind of price increase, but actively shop for alternatives. Manufacturers/developers might not want to develop a generic in the U.S., where catching up to the EpiPen would require a huge amount of marketing (significantly more costly than the production and development) just to get a small piece of that pie, whereas with the NHS they merely have to show its effective, safe, and economical. Its why its $70 for an eppipen there as oppposed to $200+ here.

Not only that, but other countries doing this increases the cost of medicine in the U.S. We're the only wealthy country who doesn't do it. At a basic level, it makes sense. If you sell Epipens in, say, Paraguay for $500, no one will buy them. Not because they don't want them, but because they can't. Their GDP per capita is less than $5,000. But they might buy them at $50, enough to make a profit. However, there is a point of diminishing returns where increasing the price will result in less profits. So when Heather "Gilded Bootstraps" Bresch becomes CEO and her goal is to increase profits... she will increase them where she can. Which is the U.S. Martin "Turing Would Hate Me" Shkreli talks about it some point in this video. He has to charge a ton for this medicine, to people that can afford it, so he can give it to people that can't, and afford to develop new medicines. Companies, apparently, have to spend money advertising because doctors are ignorant (they are--most wouldn't know about the epipen alternatives!). At least, this is their justification. The biggest reason is that they like money and more money is better than less.

There is so much money in healthcare in the U.S. that it just disappears. You probably don't pay full cost for the epipen--your insurer pays for some. You don't pay for insurance, your employer does. They don't pay for the full cost of that, you and the government probably cover a significant amount if not all of it (even if its through your employer). You possibly aren't even aware that you are having money taken directly out of your paycheck for this or not. You can check on your pay stubs. Your doctor probably can't tell you what the drug they prescribe will cost, there is a decent chance they can't actually even tell you how much you being there in person that day costs you. This goes on. Not only do doctor's have their education subsidized directly through grants, they probably have it subsidized heavily through loans. Not only does this money go to the schools in tuition and fees, the government also directly subsidizes the schools themselves. See how this goes? Still not done. Just consider, how many times you have "paid" for an epipen if you need one:

At the pharmacy.
When you pay your insurer.
When you pay to see your doctor to get the prescription.
When your taxes helped pay for all the research done to identify, synthesize, and find applications for epinephrine.
When your taxes paid to ensure the safety and quality of the product.
When your taxes created the EpiPen for NASA.

I am missing things, but I think you see my point. Healthcare is a hole where money just sort of disappears. The U.S. has the largest economy in the world and spends the greatest portion of its money on healthcare. So it is very easy to get away with these cost increases-- the U.S. is always the first choice to increase prices. Not only to increase prices, but to do so dramatically. Its always increasing. The alternative, Adrenaclick, still costs $20 more than the UK namebrand. There is so much money there, so little understanding of where it goes to, and so little responsibility for ensuring it doesn't go up that the point of diminishing returns is truly difficult to find. I imagine that Bresch felt like a kid caught with her hand in the cookie jar, but nothing happened. They raised it some more, and some more, and some more, and no one said anything, did anything, and no one stopped buying them. And who would stop them? Insurers don't care because they just raise rates, stop covering it, or come up with arcane rules to say they cover something without actually covering it. Doctors don't care, that isn't their job. The individual doesn't notice, because they have no idea where their money is going anyway, until the cost of healthcare hits them like a freight train. You don't know what an epipen costs until your kid almost dies. You going to choose your kid dying? They could increase it by another thousand, make medicare and the insurers eat it, and still not reach diminishing returns.

EDIT: I have actually edited quite a bit, but this one is a bit later just to illustrate how much of a hole healthcare spending is. You can check this out just to try and get grasp of how much we spend.

The World Bank states the U.S. spends 17.1% of GDP, $17.946 trillion, on healthcare.
Multiplied out, that is $3.068 trillion.
The next highest wealthy country, Sweden, spends 11.9%.
Lets say the U.S. brought its spending down to 13% of GDP, still significantly more than any other wealthy country. That is $2.332 trillion.
That is an annual savings of $736 billion dollars, or $2307.93 per person in the United States.

$2300 is a lot of money to a lot of people. But just to add more context on what we could collectively do with that money instead of healthcare:

There is a lot you could do with that money. It just disappears! We don't live longer, we aren't healthier, we aren't less susceptible to disease, we don't have better patient outcomes, we don't have better quality of life, we don't have better access to (better) drugs, we don't have better access to medical professionals, we don't have anything to show for all of this relative to comparable country's spending. Do this exercise yourself. It is mind blowing how much more we spend and what else we could do with it. Obviously, these things wouldn't play out perfectly in the real world, but that isn't the point. The point is to imagine what you want from your society. $736 billion, even if it just ends up back in people's pockets, is a huge amount of money that would probably go far in obtaining that. You could divide it into four, education, research, infrastructure, and defense and have it be a significant expansion for all.