If you want to understand how medical billing works and why these ridiculously high bills get created, there's a lot of important context that this article unfortunately leaves out. Large hospital systems accept patients who have a range of payers (Original Medicare, Medicare Advantage, various Medicaid plans, private insurance, and uninsured patients). On the aggregate, they want to make sure that their entire syste…
We're talking about how much the hospital has to pay its suppliers Except suppliers can engage in their own fiat prices, as the OP demonstrates. But your narrative does show the basic situation - where you have an elaborate digraph of buyers and sellers, most of which have a more or less monopolistic position. These monopolistic suppliers initially/formally set their prices based on "what they could possibly imagine…
Those aren't fiat prices by any stretch. Aside from the fact that there is a competitive market of providers, patients don't have the obligation to pay the entire billed price (a key point which this article does not mention). That's neither a monopsony nor a monopoly.
Medicare, on the other hand, is a legal monopsony over its patient population and does set its prices by fiat. (There is no competitive market; patients can opt to receive their Medicare benefits privately, but they cannot opt out of Original Medicare entirely. Similarly, most providers cannot legally opt out of accepting Medicare, in practice).