Hospital prices in the US are always lies; his insurance company probably paid around $10k in total and perhaps even less than that. Of course the insurance company doesn’t generally tell their customers exactly how much they actually paid the hospital. He could have gotten a more reasonable bill by asking the hospital for the cash price for everything, writing them a check for that amount, and then getting reimbursed by his insurance company. It might still have been more than his out–of–pocket limit, in which case he still would have paid the $2,500.
But his real mistake was probably going to the hospital in the first place. He probably should have gone to his Primary Care Physician or to an Urgent Care Clinic. Either one of them can admit him to a hospital if it turns out to be necessary, but it probably would not have been. I see in another comment that he needed an X–Ray, a CT scan, and some medication. He could have gotten all of that at an urgent care clinic for $1,000 or so, and slept in his own bed that night.
It pays to shop around, and you can do so _before_ you get hurt.
Finally, don’t forget that in addition to the $2,500 he paid, he also paid his insurance company even in years that he wasn’t injured or ill. Likewise, you pay taxes every year and part of that goes to pay for healthcare, even if you aren’t actually injured or ill.