(a) Where the permit fee is based upon the cost of the work done under the permit, such costs shall be the actual cost as certified by the owner or by the authorized representative of the owner, and as approved by the Commissioner.
(b) The Commissioner may, at any time after application for a permit is filed, up to three (3) months after completion of the building or other structure, require the submission of authoritative estimates or actual cost data to substantiate the estimated cost stated in the application for a permit, and the payment of additional fees when it is demonstrated that the actual cost of the work is in excess of the estimated cost on which permit fees were paid.