First, wow, that was a good study and well worth the read. That's not to say I completely agree with the parameters or the conclusions and I'll explain.
First let me offer my bias. I've known Charlie Collins for over 30 years and I've bought dozens of his 'skins' and other items. I've been to his home countless times and he's provided me with a wealth of hackle information (breeding, what to look/lookout for, patterns, tying techniques, etc).
Okay, now: In your price list you identify what I'll guess are the most up-to-date prices you could get. The prices represent roughly comparative items. However, you should have placed an asterisk on Collins with an explanation that the saddle is included. You do say this in the conclusion but that may be missed by readers. Also, you say that the saddle received was a different color then the neck. This, and I'm not saying this happened in your case, is a natural phenomenon. Black necks/badger saddles, brown necks/cream saddles, for example.
I'm a wasteful tier. I usually get 1 fly out of a hackle regardless of the length of the 'sweet spot'. If other tiers do the same, that would effect at least one and maybe two of your statistics.
How closely a breeder trims the neck is important if by trimming the process eliminates the side hackles used for tailing. Actually these Tailing feathers are located in the front of the bird's neck but the cutting process puts them on the outside edges. One breeder that left a lot of these feathers in tact was Denny (Conranch Hackle). But he retired recently and sold his flock.
The packs of tailing that C. Collins sells are actual 'spades' off of the scapular area. They are grabbed and plucked en mass so you do get some waste material. But most feathers will tie size 8 and smaller. And some are slightly larger and they can be used for hackle on Neversink Skaters, Spiders and Varients as well as tails.
As far as 'dyeing', as was mentioned in one post, Charlie has a special way of dyeing the skins so that the results are very difficult to notice, the underskin is not effected, and the dye does not bleed. As of my last conversation with him, he does not dye the saddles.
Anyway, great job. I have had and have most of the types(breeds) you mention and think the ones I have are all excellent for what I paid. Considering I've been tying for well over 50 years and my first necks were from Herter's, all I've got to say is, "We've Come A Long Way, Baby".
Allan