The fee for any certificate issued pursuant to the provisions of this ordinance shall be $20 and said certificate shall be valid for a period of three months from the date of issuance; except that any person certified pursuant to the provisions of this ordinance shall have the option of purchasing for $80.00 a certificate valid for a period of one year from the date of issuance. The Board of Supervisors may increase the certificate fee when necessary in order to finance the costs of the Art Commission in administering and enforcing the provisions of this ordinance.