(a) The expense of examination of an insurer or of any person referred to in § 319(2) of this title (management or control of an insurer under contract) or § 319(4) of this title (promoters, etc.) shall be borne by the person examined. Such expense shall include only the reasonable and proper expenses of the Commissioner, and the Commissioner's examiners and assistants, including expert assistance, and a reasonable per diem as to such examiners and assistants as necessarily incurred in the examination.
(b) Such person examined shall promptly pay the examination expense upon presentation by the Commissioner, or the Commissioner's examiner, of a reasonably detailed written account thereof.