Day-use parking at the park's Gulf accesses is a flat rate per vehicle rather than an hourly charge, which is now the significant difference between parking here and parking in the city lots a mile west. Recent rates have sat around fifteen dollars a day. There is no separate charge to walk in.
The detail worth knowing is that the daily parking rate has included one pier fishing permit for one angler in the vehicle. If one person in your group intends to fish, that turns a parking fee into two fees paid at once, and it is the cheapest day of fishing available anywhere on the Alabama coast.
An annual beach access permit is sold for the state park lots, recently priced around two hundred dollars, and it has to be bought in person at park headquarters on State Park Road during weekday office hours rather than online. That is worth the trip for a family that comes every year and worth nothing for a single week's stay. Orange Beach residents and military personnel have had their own arrangements.
Trail access is free, everywhere, all the time, and so is the Nature Center. The lakes are free to fish from the bank with a valid Alabama licence. Nothing on the inland side of this park costs money unless you are renting something to sit on.
Fee schedules are set by the state and revised, so check at the gate or with park headquarters before you build a budget around a figure.