Mo. Rev. Stat. § 443.360: Compensation of trustees under trust deeds.

As a compensation for his services, any person selling property at auction under any writing, instrument or deed made or executed for securing the payment of any debt shall receive a commission on the amount of sales not exceeding two percent on the first one thousand dollars, and one percent on all sums over that amount and under five thousand dollars, and one-half of one percent on all sums over that amount.