you can get a vial of epinephrine and fill your own syringe if you ever need to, but you have to specifically ask a doctor to prescribe that for you. you can't substitute a vial of epinephrine for an epipen script even though it's the exact same thing.
and because our medical system likes to pretend that cost is completely irrelevant to medical decisions, basically no american doctor ever asks their patient - hey, would you prefer a script for a $10 vial of epinephrine or for two $600 epipens?