Obviously the benefit is greatest for items based on 2nd level effects, but it still provides a small noticeable savings as shown below
1st 0.0%
2nd 33.3%
3rd 20.0%
4th 14.3%
5th 11.1%
6th 9.1%
7th 7.7%
8th 6.7%
9th 5.9%
The only other thing i might add is that although you have the pieces in place, you don't seem to have factored in the important key that Enhance item is an [item creation] feat, which serves us well when combined with the Magical Artisan Feat. Example Below
Feats | | | | | Time | Gold | XP | | Time | Gold | XP |
1 | Exceptional Artisan (Time) | | | | 075 | 1 | 1 | | 075 | 1 | 1 |
2 | | Enhance Item | | | 1 | 1 | 1 | | 075 | 1 | 1 |
3 | | | Magical Artisan | | 075 | 075 | 075 | | 05625 | 075 | 075 |
4 | | Magical Artisan | | | 075 | 075 | 075 | | 0421875 | 05625 | 05625 |
5 | Legendary Artisan (Xp) | | | | 1 | 1 | 075 | | 0421875 | 05625 | 0421875 |
6 | | Enhance Item | | | 1 | 1 | 1 | | 0421875 | 05625 | 0421875 |
7 | | | Magical Artisan | | 075 | 075 | 075 | | 0316406 | 0421875 | 0316406 |
8 | | Magical Artisan | | | 075 | 075 | 075 | | 0237305 | 0316406 | 0237305 |
9 | Extraordinary Artisan (Gp) | | | | 1 | 075 | 1 | | 0237305 | 0237305 | 0237305 |
10 | | Enhance Item | | | 1 | 1 | 1 | | 0237305 | 0237305 | 0237305 |
11 | | | Magical Artisan | | 075 | 075 | 075 | | 0177979 | 0177979 | 0177979 |
12 | | Magical Artisan | | | 075 | 075 | 075 | | 0133484 | 0133484 | 0133484 |
13 | Specific Item Creation Feat | | | | 1 | 1 | 1 | | 0133484 | 0133484 | 0133484 |
14 | | Enhance Item | | | 1 | 1 | 1 | | 0133484 | 0133484 | 0133484 |
15 | | | Magical Artisan | | 075 | 075 | 075 | | 0100113 | 0100113 | 0100113 |
16 | | Magical Artisan | | | 075 | 075 | 075 | | 00.75085 | 00.75085 | 00.75085 |
|
Which then adding the some of the other listed reductions, say
Specific Skill Requirement
Specific Class or Alignment
Apprentice, Craftsman
Colossal Elemental Binding
Favored in Guild
Bulky but Technically Removable (SBG, Pg 70)
Darkspire College
Extract Demon Essence
Quick Crafting (Maester)
We Get the final numbers of
2.37% Time; 1.46% Gold; 2.13% Xp
Double that for normal items, Halve that for immobile items, Quarter that for rune circle versions of items on a 5ft square. As a partial maximum General Reduction, before adding in all the specific modifiers or a couple of the generals i didn't toss in.