In establishing and maintaining the rates, charges, and rentals authorized by the provisions of this chapter, the Department shall give due consideration to the debt service requirements of the bonds or obligations of the Department for the payment of which such rates, charges, and rentals are pledged and, in addition, it shall give due heed to the cost of operating and developing said island and the various facilities and services maintained thereon. It shall likewise give due consideration to depreciation and the cost of replacements and the cost of additional improvements and facilities. Any surplus in revenues that may be derived after deducting debt service charges, cost of operation and maintenance and cost of additional improvements and facilities and such further sums as prudent management requires to be set aside for depreciation and replacements shall be paid one half to the county of Beaufort in accordance with existing statutes and one half to the State Treasurer. The State Treasurer shall credit such moneys received by him to the park fund already provided for the use of the Department in the furtherance of the State park program.