How do I apply the reductions on magic items?

[Senko]

Can't find an answer on this so I just figured I'd ask. Lets say for arguments sake your crafting an item which requires a specific skill and a specific class (something I don't like doing but that's another topic) and apply those to an existing item e.g. ring of invisiblity how do you do that?

So we have the ring of invisibility costing 10k from the base 50% discount and I then apply a 10% and 30% discount which is where I'm not sure how they stack is it

A) 50 + 10 + 30 = 90% = 0.1 x 20,000 = 2,000 GP to craft.

B) 10 + 30 = 40% = 0.6 x 10,000 = 6,000 GP to craft.

C) 20,000 x .5 x .7 x .9 = 6,300 GP to craft.

D) Something else I'm missing.

I'm leaning towards B myself but does anyone know the rules on this?

EDIT
Throw in spark of creation for an extra 5% giving you . . .

Crafting Cost: 50%.
Requires class: 30%
Requires Skill: 10%
Spark of Creation: 5%

I'm pretty sure you don't reduce the cost by 95% of the sale price especially if there's anyway to get another 5% you'd reduce it to 0% and get it free. Still thoughts?

[Theaitetos]

Senko wrote:

Requires class: 30%

Requires Skill: 10%
Spark of Creation: 5%

These reduce the base cost of the item, not the crafting cost. Crafting is always 50% of the base cost (or 1/3rd when using a Craft-skill).

The Ring of Invisibility has a base cost of 20k gold.
In your example, reduce this base cost by 45% (= 30% +10% +5%) to 11k gold; that's your new base cost.
Crafting this item costs you half of that, i.e.: 5,500gp.

You should always calculate the reduced base cost first, before applying the 50% crafting reduction, because you might need the base cost for other calculations (downtime, ...).

[Scott Wilhelm]

You also don't include the price of the nonmagical item before enchantment.

I know this because a Maul of the Titans costs 25,305 gp. It is a reduced price magic item: you can't use it unless you have an 18 Strength or higher. It is treated as a +3 Masterwork Greatclub that does triple damage vs. inanimate objects. That 18 Strength requirement means it costs 10% less than it otherwise would.

Well, a nonmagical Masterwork Greatclub costs 305 gp. That means the 10% dicaount can't have included the initial 305gp for a Masterwork Greatclub. That means the price of creating a Maul of the Titans without that 18 Strength limitation must be 25,000gp X 10 / 9 = 27,777gp, 7sp, and 8cp.

Likewise a Shatterspike is a +1 longsword that does an extra +3 Attack and Damage when used to Sunder, but you have to have Improved Sunder to use that feature. It costs 4315gp, and a nonmagical masterwork long sword costs 315gp. So a Shatterspike that does not require the wielder to have Improved Sunder costs 4000 X 10/9 = 4444gp, 4sp, and 4cp.

Because sure, those number say loud and clear that the Paizo Design Team pays attention to their own rules!

[Senko]

So option D then ok that's not how I'd have done it thanks.