It's what the traffic will bear.
The cost is in the patented injector, the drug itself is cheap. Others have tried to market similar injectors, which didn't work as well as the Epipen.
As cost slowly rose, insurance paid for it, and parents didn't notice it as it was hidden in rising insurance premiums. Then deductibles skyrocketed, and suddenly insurance wasn't covering it all; parents had to pay the balance, or all of it.
If you didn't have insurance, you already watched it go up as it happened.
Finally the cost was raised arbitrarily, to cover the company's coming losses as their patent on the delivery system will expire. This, I've read recently, is common: a spike in price before generics take over.
The traffic bears this price, because parents don't want their kids to die from accidental exposure to peanuts and other allergens.