I briefly worked in adjacent space. While I hate the way it works, it makes a lot more sense when you understand that the billed amount is essentially just a negotiation tactic that represents a price well above what they ever expect to be paid (and a bit added to that for safety).

Then, they negotiate with all of the in-network providers for some number that’s well below the billed amount. That number varies a bit based on how effective various negotiations are.

Realistically, OP simply found the number that insurance was going to pay out anyways.