And yes, in some cases the extra stopp is worth twice (or more) the price. It might make the difference between getting the shot, and getting a blurry mess. OTOH,
Usually worth it for pros who make money from those valuable shots. When I get a blurry mess I just bin them and try again another time. So it just depends how much you value those shots you missed at F4. Also depends how rich you are of course 

