Exceptional/Extraordinary/Legendary/Magical Artisan {ECS/PGtF}
Reduce the crafting costs (Time/GP/XP) for crafting Items. Extraordinary and Legendary are both necessary for reaching 100% cost reduction before epic levels. Exceptional is not all that useful sense Scroll can be made quite quickly anyway (only useful for Scrolls with six 9th Level spells, for example), but the reduction is not much. Magical Artisan applies to a specific Crafting Feat and applies to all costs, great for Wizards which normally only have Scribe Scroll anyways, but do not it does not directly stack with the other Artisan Feats or USs Master Scribe ability (though you do get to calculate cost reduction of 75% the normal cost of the item). Useful at lower levels but should be retrained once you hit 100% efficiency.
Cost reductions do not add together since cost is a real world value and thus you use real world math (not dnd math). As a result, you can never craft for nothing (except in specific circumstances where it says to subtract a specific amount of gold). For example two reduction of 25% do not result in you crafting for 50% of the price, they result in you crafting for 56.25% of the price (100-0.25*100=75, 75-0.25*75=56.25)
Edit: For advice on crafting cheaply see my handbook (link in my sig).
Master Scribe specifically states it stacks with Extraordinary and Legendary Artisan though. It even shows an example of a 5th level Unbound Scroll with Legendary Artisan crafts scrolls with a 50% reduction to XP cost.
So a character with effectively 13 levels in Unbound Scroll and the two Artisan Feats has 100% XP and GP efficiency in crafting scrolls (the last 10% comes from the resources section of Unbound Scroll which states it has an additional 10% reduction of crafting which stacks with Artisan and Master), unless there is something I am missing.
EDIT:
Yeah I have taken a look at your Guide, which helped me find the Quill of Scribing which is just great.