Costs of publication and public notice shall be borne by the sponsor of the petition. The estimated cost shall be paid by the sponsor to the Auditor at the time of validation of the mini-initiative.

If the actual costs are less than the estimated payment, the difference shall be returned to the sponsor. If the actual costs are greater than the estimated payment, the sponsor shall forthwith pay to the Auditor the difference, upon written notification of that underpayment.