The fee shall be based on actual costs to assemble the Board of Examiners. A fee as provided in Section 80487 must be paid prior to the scheduling of the examination. After actual costs have been determined, a refund of any unearned portion of the fee will be paid to the applicant. These costs may be prorated between two candidates when two candidates are to be examined in one day, and among all candidates taking the same examination when the examination session lasts longer than one day.