However, if the doctor is outside of insurance network, he can charge patient whatever amount he wants to charge. Depending on the policy, insurance will pay certain percentage of what they think is reasonable. The patient has to pay the remaining.
It is always a good idea to know how much the doctor will charge before your visit if s/he is not in the network. Also, one can try to negotiate with the doctor to a reduced amount. After all, if the doctor sells the bill to collecting agency, he won't get much himself anyway.