If a Medi-Cal provider negotiates a rate of payment for inpatient, outpatient, or ancillary services with a prepaid health plan under contract with the department pursuant to Chapter 8 (commencing with Section 14200) of this part which is lower than or equal to the lesser of reasonable costs, customary charges, or the schedule of maximum allowances, the rate shall not affect the director’s determination of reasonable costs, customary charges, or schedule of maximum allowances.