one paragraph here points to a dirty little secret about how Medicare pays hospitals, I found out researching this for family in 2007.

Perez took advantage of federal health care regulations that allow some rural hospitals to bill for laboratory tests at substantially higher rates than other providers. The goal is to keep hospitals that provide vital care in remote areas afloat, by paying generously for the relatively small number of tests needed in such locations.

Except it's not just rural, they incentivize amount of payment for all kinds of criteria, I read articles explaining how they do it for distressed urban areas too, that they adjust what they pay for recidivism per patient for certain illnesses, how many uninsured the hospital takes, stuff like that. People think Medicare is paying the (often ridiculous) individual bills that are printed out. They aren't, they are giving hospitals something much more like lump sums. I.E., so many dollars per so many diabetic-related amputations, so many dollars per code per day. Medicare payment to hospitals is not on an individual patient basis at all.

I have no idea about how the supplemental insurance fits in here. They may be where the ridiculous individual bills come in. As one reads about how they are negotiating contracts with the hospitals, too. And if is an Advantage Plan that's like an HMO offering more than Medicare does in exchange for a limited network of providers, A big company like United has a myriad number of plans, they have plans with employers, they have Obamacare plans, they have Medicare supplemental plans, they have plans managing Medicaid with states. I have more than an inkling they are the main payer and then get reimbursed by Medicare and Medicaid.  So an entity like United sits down at the negotiating table with a hospital and talks about paying something for all its patients in all its plans. And then gets payback from Medicare and Medicaid for those patients? It gets so complicated it can make your head spin.