The amount of state aid given a fair under Section 2-7-27 shall be a percentage of the prizes or premiums paid by the fair. In no case shall a fair be paid state aid and merit awards combined exceeding the amount such fair pays in approved agricultural prizes or premiums. The total amount paid by the board in state aid and merit awards to a fair in any year shall not exceed the amount authorized herein. No allotment and payment to a fair under Sections 2-7-26 and 2-7-27 for state aid shall exceed 50 percent of the prizes and premiums paid at the fair, and no such fair shall be eligible for an allotment unless at least $500.00 is to be paid by it in prizes and premiums. No part of any allotment and payment of funds payable hereunder shall be used for maintenance, improvements or operating expenses of any fair or for any other purpose than prizes, premiums and awards.