The chief of police is empowered to establish fees for the use of the city polygraph instrument and polygraph examiner by other governmental entities. Such fees shall be filed with the office of finance director and the finance director shall collect the fees prescribed. In setting a fee schedule, the chief of police shall set a rate that, at the minimum, will cover the costs of the city of Aberdeen in providing this service. Such fees shall take into consideration the examiner's salary, travel time, witness fees, and other expenses. Use of the polygraph instrument for private enterprise is prohibited.