SRD Talk:Armor for Unusual Creatures
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Calculating Armor Costs for Unusual Creatures Using Special Materials
According to the FAQ, the armor cost multiplier for unusual creatures is applied after the base price and the added cost for the special material, but before the cost of masterwork. This makes things a bit difficult with every special material except cold iron and alchemical silver, since the material costs already include masterwork costs. The FAQ suggests a little reverse math is in order.
The FAQ uses mithral chainmail barding for a heavy warhorse as an example. Medium mithral chainmail for humanoid-shaped creatures is 4,150 gp: 150 gp for the cost of chainmail plus 4,000 gp for the cost of it being mithral medium armor. Since the cost for it being masterwork is already included it has to be subtracted before multiplying by 4 (for Large nonhumanoid).
4 × (4,150 gp − 150 gp) + 150 gp = 16,150 gp.
Not quite the same as what's in the FAQ, because upon closer inspection, it becomes clear that the FAQ forgot to add the masterwork cost back in after the multiplier. —Sledged 13:50, 16 January 2007 (MST)