I would have to agree with Mark on this.
Look at it this way, I played a 910 D2 with a 72 gram 'Ahina shaft stiff flex. I also played a Ping G10 with a Proforce V2 x-stiff shaft. I hit both extremely well, and the same distance, and similar consistency.
Given the Titleist club felt WAY better to me.
Basically it is what Mark is talking about. The golf swing matters more. If you find a shaft that can tighten the variable a bit, then it can be an advantage. Minimal from a numbers stand point, but mostly from a feel and confidence standpoint.
There are PGA tour players who play $300+ dollar golf shafts, and there are some who play Proforce V2, which is sub $150 dollar shaft.
For most people, they certainly aren't worth it.
There's a guy named Tom Wishon, who is one of the more knowlegable guys in the industry (notable club designer, researcher, and author of best selling books on golf equipment) who regularly comments at GolfWRX, and he basically says, flex and bend profile matters "a little, but not even close to as much as what you can do for the average golfer with the best fit for his length + loft + face angle + shaft WEIGHT + swingweight."
And even with regard to feel, which can be impacted by these flex and bend profile differences, Wishon says you can also match "feel" if you match bend profile, weight, torque and balance point. And that the bend profile of that expensive new shaft can quite often be matched by a less expensive or older design. And he has apparently done lots of scientific testing which backs that up.
Yes obviously, I did watch it. Still would like to see how it affects a higher handicap golfer. What shaft variances make them more and less likely to be able to do that. Seeing a pro hit a bunch of different shafts should produce predictable results. Just saying fix your swing is a common answer and many think club fitting benefits the more skilled golfer, and I would agree. Still would be interesting to see it they could find something best suited to a lesser skilled golfer if it's even possible.
If you've ever been fit you probably noticed some shafts just felt bad for you and others better. Mark kind of splits hairs here. While 6 yards and two degrees may be a mile of difference to him a poor golfer probably sees a 100 yard difference between their best and worse drives on any day. What I'd like to know is if being fit for a shaft tightens it up a bit for that golfer. Say take 3-4 of their swings where the swing numbers are somewhat close and see how different shafts change the ball numbers.
Have you ever been fit?