ProPublica has been researching why the U.S. health care
    system is the most expensive in the world. One answer,
    broadly, is waste — some of it buried in practices that
    the medical establishment and the rest of us take for
    granted.  We’ve documented how hospitals often discard
    pricey new supplies, how nursing homes trash valuable
    medications after patients pass away or move out, and how
    drug companies create expensive combinations of cheap
    drugs. Experts estimate such squandering eats up about
    $765 billion a year — as much as a quarter of all the
    country’s health care spending.

    Tossing such drugs when they expire is doubly hard. One
    pharmacist at Newton-Wellesley Hospital outside Boston
    says the 240-bed facility is able to return some expired
    drugs for credit, but had to destroy about $200,000 worth
    last year. A commentary in the journal Mayo Clinic
    Proceedings cited similar losses at the nearby Tufts
    Medical Center. Play that out at hospitals across the
    country and the tab is significant: about $800 million
    per year. And that doesn’t include the costs of expired
    drugs at long-term care pharmacies, retail pharmacies
    and in consumer medicine cabinets.

(I do agree with your point that most of the cost, and especially the most egregious examples like the wasted epi-pens, don't represent real costs because of monopolies.)