To periodically establish a discounted fee or fees for the entry and use of selected state parks and recreational facilities. The discounted fee or fees shall only be used for the purpose or purposes of marketing and promotion to increase the patronage and revenue of those selected parks and facilities. The discounted fee or fees shall not be considered a donation of state property. Each park shall retain from revenues generated therein, a sum sufficient to pay necessary expenses of operation, but in no event to be less than seventy-five percent (75%) of such revenues.