The same procedure in the same hospital can settle at very different amounts depending on the patient's insurer. The difference is contractual rather than clinical.
The list price is not the transacted price
Hospitals maintain a chargemaster, a list of billed prices covering every item and service they provide. Almost nobody pays those figures, and they bear little relation to what the care costs the hospital to deliver.
Insurers negotiate discounts off those charges, or fixed case rates that cover a whole episode, and the negotiated figure is what the claim actually settles at.
The chargemaster matters mainly as a starting point for negotiation and as the amount facing someone with no coverage at all, which is why uninsured patients are often quoted the highest number in the system.
A network is the negotiation itself
A network is the set of providers that have signed a contract with an insurer, and that contract sets the rate the insurer will pay for each service the provider performs.
Providers accept lower rates in exchange for patient volume steered toward them by the plan's benefit design, since being in network makes them substantially cheaper for the member to visit.
Narrower networks generally secure deeper discounts, because the volume promise behind them is more concentrated among fewer providers.
Leverage decides who gets which rate
A dominant hospital system in a region can insist on higher rates, because an insurer that excluded it could not sell a credible plan to local employers whose staff already use it.
A large insurer holding most of the local membership has the reverse leverage over a small independent practice, which cannot afford to be outside the plan that covers most of its patients.
Rate variation between insurers in the same market usually reflects that balance rather than differences in quality.
Out-of-network care leaves the contract behind
Without a contract there is no negotiated rate, so the provider bills its own charge and the plan pays what it deems allowable.
The difference has historically been billed to the patient, and rules limiting that practice vary by jurisdiction and continue to change.
This is why the network status of the facility, the surgeon and the anaesthetist should each be checked before a scheduled procedure.
Published rates have not flattened the differences
Requirements to disclose negotiated rates have made some of this visible, but the files are large and service definitions are inconsistent between them.
Comparing two published rates often means comparing different bundles of billing codes rather than the same operation.
An insurer's estimate for a specific planned procedure remains the more usable number, because it applies the member's own benefits to the contracted rate.