This scale would provide daily productivity on a project. The DM would determine the basic value of the intended item if it were mundane. Once enough productivity is achieved, then the item is created and its’ overall quality is checked. It is reasonable to say that a Full Set of Plate Mail would take even a highly skilled, High level Smith a LOT of time. With this scale, I would expect that smith to complete the work inside of 100 - 150 days of working 8 hours each. A rushed job might take less time, but the expected fee would increase. Meaning, the cost of materials would go up. In reality, Full Plate was often a lifetime of work for a single smith. Thus, one could say 300 days in generous already. However, Armor was rarely an individuals work. Rather, it was often made by teams of smiths with each person working on a specific part they specialized in. Thus, 8 smiths making Chest, Back, Left Grieve, Right Grieve, Left Hand Glove, Right Hand Glove, and leggings separately could build the armor much faster. They would need 10-12 days to complete the order.
The DM determines which tool or tools are necessary. The DM determines which skill bonuses will be relevant at which point in the creation process. Each item, mundane or otherwise, should have a recipe made by the player and agreed upon by the DM. The Cost of Materials should not exceed half the item's sale value.
Example: Long Sword - Sale Value = 15 GP. A Recipe may look like this... 5gp of Steel, 1gp of Leather, 5sp Wood, 1gp other materials as needed.
DC < 5 = loss of investment and time
DC < 10 = 1 GP worth of productivity
DC < 15 = 5 GP
DC < 20 = 10 GP
DC < 25 = 15 GP
DC < 30 = 20 GP
DC < 35 = 25 GP
DC 36+ = 30 GP
Then I might do a qualitative scale for a final check.
DC < 15 = flawed
DC < 20 = Mundane
DC < 25 = +1
DC < 35 = +2
DC 36+ = +3
As far as enchanted equipment is concerned, I am tempted to stick with what I know. Each Tier above 2 Requires a Star Stone from the correct school relative to the enchantment being applied. They might require rare items like Dragon Hearts, Mummy Dust, or what ever would make sense for the enchantment. That would be DMs Discretion.
Tier 1 Temporary Enchantment - can be cast on any item and lasts for a very limited time say 10 minutes.
Tier 2 Charged Enchantment - Requires Enchant Item - The items only carry the charges on the item. Once used, it becomes mundane. Requires a +1 item
Tier 3 Rechargeable Enchantment - Requires Enchant Item and Permanency - Items can be recharged under certain conditions.
Tier 4 Items with permanent effects - Requires Enchant Item, Permanency and either limited wish or wish
Tier 5 Items with multiple permanent enchantments - Requires Enchant Item, Permanency, and Multiple Limited Wishes to be paired with a regular wish. - Think the best of Magic Items in the DMs guide that are not relics or sentient.
Tier 6 Items of Legendary Status - Requires Enchant Item, Permanency, and Multiple Limted Wishes to be paired with a regular wish AND other to be determined resources relative to the abilities of the item. - Think Sentient Weapons, Dragon Orbs, and other Legendary items.
Anything above tier 2 would require at least a +2 Quality item for the process to work. There would also be a research and planning requirement.
For Chomsky, a Tier 6 Long Sword would likely require a couple days (Call it a week) to create a +3 Quality Long Sword (multiple tries would likely be necessary to hit the 40 DC Required even with Expertise in Smithing and bonuses granted from Magical Crafting Gear.) Then, he would have to research the spells for the desired effect and source them. That would be a week of study. Creating Limited Wish and permanency one time use Boxes takes a day each. He must have a Wish box made OR have a charge in his ring to do so. That requires a month of time. He would need to buy or acquire the necessary items which would also include a soul for a sentient weapon. Lets assume he could manage acquiring the missing ingredients inside of three months.
Weapon Target is: +3 Longsword which is Intelligent and has a N or Good leaning. Perhaps it has one drawback like it will not serve a (qualifier here) master. However, it might have a minor effect like dealing 1d4 Lightning damage and a major effect of casting Chain Lightening once per day.
Recipe
1 +3 Quality Long Sword
1 Wish Box
3 Limited Wish boxes
1 Permanency Box
1 Soul from an intelligent being
1 Casting source for Chain Lightning
1 Enchant Item Source
1 Shocking Grasp (for the lightning damage effect)
1 Black Star Sapphire (For Magic Jar Spell)
2 Star Jacinth (One for Chain Lightning and one for Shocking Grasp)
Estimated Cost for the Build:
5,750 GB for Sword +3
100,000 GP for Wish Box
60,000 GP Limited Wishes (3)
20,000 GP Permanency
10,000 GP Enchant Item
5,000 GP for Black Star Sapphire
10,000 GP for 2 Jacinth
Undetermined - Soul
Total = 210,000 GP and about 6 months worth of time all together.
Result = +3 Sentient Long Sword aligned with the original soul. Those of a different alignment can not attune the item. It also gives 1d4 in lightning damage on successful attacks and can cast chain lightning once per day.