They are priceless!! If they are in fantastic condition you have something great. If they have writing on them or are beat up they are worth a less.
You may need to special order it, as they may not export
Glass or Carbon fiber on styrofoam
foam interior, for boyancy, fiberglass exterior. Now, some surfboards are made with special polymers. When repairing a surfboard though, it is general practice to use fiberglass to patch the injury
G'day Jake L, Thank you for your question. Surfboards were originally made of wood or balsa. These days they are mostly made of polyurethane or polystyrene foam covered with layers of fiberglass cloth and polyester or epoxy resin. However, there are some specialty boards made out of aluminium and carbon fibre. I have attached sources for your reference. Regards