Super Tuna
You can't scale this!
Does that make a significant difference?
Honestly? I don't know. When you talk to Talamonti he makes a convincing argument. When I try it out myself on the Spine/FLO side, I don't see any difference. On the frequency side, I believe that's very important. Just because you order 8 shafts in stiff flex, doesn't mean that's what you get. KBS has the best tolerance for that by far or one can pony up for the "Tour Issue" dynamic golds (which really just means they've been weighted and flex tested by hand. Usually it's 200 shafts out of a batch of 2000. Then they just label the rest of the batch by the average flex rating of the ones done by hand).
It's dead easy to get 8 shafts and have 5 of them be to flex while the other two are off. Presuming you want a consistent flex for consistent results, those shafts are going to have to be altered one way or another to sort it out. IMO, I consider this rather important and a requirement of having a true "custom" set of irons built for me.
I like to do the work myself when possible and it seems as though it will save me some money. Now I will bot be able to weigh the heads or cycle the shafts, but do I need to? How much of a role does that make?
That depends on how precise you want the irons to be. Will you personally see a difference between a set build to ultra tight specs and one that's not? Maybe, maybe not. If you're ok with maybe not, then no worries. I have nothing against people doing the work themselves nor saving money. In fact, I wish more people would. That being said, you're first post looked, to me, like you were leaning towards a truely custom set of tuned irons. Unfortunately that does not go hand and hand with saving money usually.