"the Mylan pharmaceutical company has jacked up the prices for an EpiPen — the portable device that can stop a potentially life-threatening allergic reaction — from around $100 in 2008 to $500 and up today"

NBC:

Following a recall by Mylan's chief competitor last year, the company now enjoys a near monopoly.

...

And because they have a stated expiration date of one year, parents refill them annually, incurring an additional co-pay each time.