I believe there are three alternatives: Epipen, Adrenaclick, and Twinject. The FDA does not allow pharmacists to substitute one for the other at the pharmacy, and many (doctors and patients) opt for the best-known brand.
My understanding is if the prescription says "EpiPen" (or any non-generic drug brand name) the pharmacist must provide an EpiPen (or the brand-name drug). If the prescription says "epinephrine auto injector" or "EpiPen or generic," then the substitution is allowed.
> Are the products that different?
IIRC, they all the current alternatives deliver the same medicine, but they use different injector mechanisms to do so. I think the last alternative withdrew from the US market for some reason, because their mechanism wasn't as reliable with dosing.
IIRC, EpiPen's mechanism is apparently off-patent, so a true generic could enter the market if approved.
What is preventing other companies to come to market with cheaper versions of the EpiPen? Why are there no cheaper alternatives?