The Department of Mental Health shall establish the charges for maintenance and medical care for patients, other than beneficiary, of State mental health facilities. These charges shall be based upon the per capita costs per day of the services rendered, which may include costs of operation, costs of depreciation, and all other elements of cost, which may be adjusted from time to time as the Department of Mental Health considers advisable. It shall establish a reasonable scale of fees to be charged patients, other than beneficiary, served by the mental health clinics and shall retain these fees for use in defraying the expenses of the clinics.