A stock Tensei White shaft vs an upgraded $900 auto flex shaft .The reason the auto flex is so expensive is because it is made in a way that adjusts its flex to suit any club head speed (within the recommended limits) getting as much out of someone’s swing as possible .They are quite light and feel whippier than a standard stock shaft so control can sometimes be an issue with them although a lot of people do claim that it gives them extra yardage .I personally don’t see too much of a difference

AutoFlex SF305X vs SF405 For Slow Swing Speeds