The governing authority of any municipality or district may include in the maintenance cost of any sewerage or garbage district a sum sufficient to allow to the tax collector of the parish the same commission on the amount of the annual charges collected by him hereunder which the tax collector ordinarily receives under the existing laws for the collection of ad valorem taxes, and a sum sufficient to reimburse to the municipality or district and to the tax assessor the extra expense to which these authorities are subjected in levying and collecting the charges, the amount of which reimbursement in each case is to be fixed and determined by the governing authority.