A place to leave boat for a couple of months in SC or GA
Brunswick Landing Marina in Brunswick is $7.50 a foot, no contracts. Great hurricane hole.
Next cheapest southward would probably be Ortega River Boatyard in Jacksonville, also $7.50.
Further down the St. Johns is Green Cove Springs marina. They never seem to have any space, but their rates are very low, last year they were around five bucks a foot (I think).
I don''t think "Florida" marinas are too expensive until you get south of the Sebastian/Jupiter zone. Then you start paying through the nose during season (I peaked at $18 a foot once, but you can hit $24 a foot in Key West).