Yes, under Part B

I recently had joint replacement surgery of the carpometacarpal joint (base of thumb) and carpal tunnel surgery at Ocala Regional. It was an outpatient procedure. The cost? $85,000. Medicare will only pay what the mean average is for this area and these procedures. Depending on the area that average could be greatly different. 80% of that given amount will be paid by Medicare, the remainder of 20% will be picked up by my secondary insurance which is United Healthcare. My guess is that it will be much less than $85k.

What do you mean the cost is $85,000? Whose cost? If the surgeon and the facility accept Medicare, then the cost is whatever Medicare agrees to pay. There is no other cost.

Start by going to Medicare.gov and look at your EOB (Explanation of Benefits) for your stay. The EOB will show the date of the hospital stay, but the EOB will probably be dated 1-2 months after. You will see there what Medicare paid for and what was submitted to your UHC supplement. You didn't state which supplement plan you have, but you can see what they paid for out of what was submitted to them from Medicare. Then you can look at your supplement EOB and see what was submitted to them and what they paid. If you have UHC "F" plan, they pay all "Medicare approved charges" that Medicare didn't pay. Note that if Medicare didn't approve the entire amount, which they almost never do, the supplement isn't required to pay any of the unapproved amount, either. If for some reason any of the providers at the hospital (radiologist, pathologist, etc.) aren't participating (yes, that can happen, rarely, but it does) then you will get a bill from them. But as long as it says you don't owe anything on your EOB then they shouldn't come back and charge you.

Be aware of providers that don't accept Medicare doing business with places that do. I went to an off site hospital ER one time and had to be transported to the main hospital by ambulance. They wouldn't allow hubby to take me even though I wasn't that sick. The hospital CHOSE and called the ambulance service, but never said that it wasn't participating, even though the ER was. I ended up with a huge bill that I had to fight for about 6 months until I finally convinced Medicare that I had NO choice in the ambulance and wasn't told they didn't participate. What a pain.

Yes, pricing is ridiculous. I used to work for a company who sold medical laboratory equipment so I knew how much the hospitals paid per test. And how many "free" tests, i.e. free reagents, the lab got. Believe me the average of what they paid us for the reagents was mere pennies compared to what they got from insurance companies.

The only one that pays that high price is the soul that has no insurance. Believe it ? They will sue them for all that dough.
Such a racket.

"They wouldn't allow hubby to take me even though I wasn't that sick. "

F --- them, drag her out the door and in your car. It's a racket.

See if they can get the sheriff or LEO to stop you.

This thread just reinforces what I've seen in 35+ years of practice...

Most people have NO IDEA how their health insurance (including Medicare) works...

It sounds like one or more of the charges were denied. The hospital would have to appeal with Medicare if that is the case. You can always call Medicare because their Explanation of Benefits can be confusing.

Hospital Profits
 

You can lookup a non-profit hospital's income tax return. It is a form 990. Latest available are a couple of years old. You'll find many make a 20% - 30% profit margin (a non-profit calls it excess). It is all a billing strategy. The hospital has to bill that much because some insurances will pay that; which makes up the difference for very low payors.

After re-reading the OP's post, something doesn't seen right with their numbers...

Why would they pay $107.28 if they only allowed $37.00?

You're not reading the EOB correctly...

Another rant today from me -

A few years ago (2021) my wife had a serious issue and we went to the free-standing Ocala Emergency Room on 466A. They transported her to their associated hospital in Ocala, when we got the EOB for the incident there was a line item charge of $28,060.25 of which Medicare Approved $0.00 and her Plan F paid the $1,484. deductible on that line item.

On same EOB was another significant event, but the front page of the OB showed;
Total amount billed 65.541.
Medicare Approved 3,103.
Plan F paid 3103. (includes 3 or 4 days in hospitals)
You May Owe -0-

So what's wrong with this system ?!?!?!?!?

Obviously. $37 wouldn't even pay for a Kleenex tissue at a hospital. $107.28 "may" cover it.

Usually, yes, but it could be a limited dollar amount or limited number of visits.

There’s Medicare and then there’s Medicare. Please note that there is Medicare Part A (hospital coverage), Medicare Part B (physician coverage) and Medicare Part C (Medicare Advantage Plans, ie. Medicare farmed out to commercial insurance carriers). Each has their own rules of what they allow, with Medicare Advantage plans varying the most from one carrier to the next and even from one plan to another within each carrier.