If you go to campgrounds that are Good Sam members the 10% will pay off. We are life members so we paid for our membership years ago with discounts.
State parks depend on the state many do not offer any discounts. You would have to check with your state.
KOA parks are higher priced overall than many parks but if you use them.......
Bottom line depends on how often you go camping and where will determine whether a discount will pay off or not. Only you can determine that.