Got a stent, was in the hospital three days. My total charges before adjustments and payment by my Advantage provider, came to $81,668.38. I paid $885.00. I did have about a $45 co-pay each time at cardiac rehab, but that wasn't too bad.

copay of $1000.

A, B, C, etc.?
We have N.

Started with private plan Medicare Part B which covers doctors visits also Medicine - Part D, I suppose.

Then a couple of years ago they had to change to Medicare Advantage which means the private insurance is now Medicare. Used to be that when the Medicare would pay, say, for hospital stay, the rest would be covered by the private insurance and with our copay. Now Medicare is out of it.

For example, for years ago spouse had a knee replacement surgery. The hospital for three days charge was $42,000,, Medicare paid $13,000, private insurance $1,100 and our co pay was $200.

Even then I wondered, on these pages, whether the hospital really needs $42,000, how come it can survive with $15,000.

You say "they had to change...". Who is 'they' and why did 'they' have to change?
I'm unclear.

(and I am not even sure what this means.)

So many had o switch to Advantage and while doing that reshuffled providers and networks and whatnot.

My primary physician was no longer in the network so I had to switch carrier. In the long run I think that I am better off. Spouse stayed with the same carrier which, as I stated in the op, also owns a vast network of clinics and specialists and, perhaps the hospital.