It is more a billing negotiation tactic between your health insurance company and the medical facility that you are seeing.

The insurance company negotiates the bill to a rate of $x for in network $y for out of network. So no they are not expecting you to pay that $6000.

I got a bill from my therapist for $430 for a 30min appointment, insurance paid $186 with zero copay, it just had to go through the magical cost-reducing power of an insurance company.

This system is wierd.