My Druid player wishes to get medium armor for his large cat animal companion. I'm a little shaky about what I've read for doing this in my Society game (if it's at all possible). I had two questions on it.
Does the animal need proficiency with the armor?
He wants to make masterwork. When doubling the cost for barding, do you add the masterwork cost before or after?
(any pointing at page numbers would be most useful.)
Armor proficiency is more want than need.
Animals are normally not proficient with armor. As per PRD Armor Proficiency feat:
Normal: A character who is wearing armor with which he is not proficient applies its armor check penalty to attack rolls and to all skill checks that involve moving.
Usually only light armor (leather or masterwork studded leather, mithral kikko) is worn with no proficiency, but it is up to you to decide if the benefit of having more armor outweights the cost of armor check penalties. For example, a Mithral Full Plate has armor bonus +9 and armor check penalty -3. In Pathfinder, you can spend three feats to get Light Armor Proficiency, Medium Armor Proficiency and then Heavy Armor Proficiency to limit applicability of this penalty, but you do not have to.
Masterwork cost is added after everything else.
So, for a large quadruped, the cost of armor is: final_cost = base_cost * 4 + 150gp (this gets a bit tricky when you consider special materials, which have masterwork cost built-in, but reverse-engineering works).
Yes, he does require proficiency in the armor worn, the same as any other wearer of armor, and with the same penalties. (The rules requiring such proficiency (p. 150) make no mention of dependency on being a humanoid, or being an animal companion, or any other difference likely to apply between most armor wearers and your animal companion.)
Ambiguous. The RAW, strictly read, does not specify which of these to do. However, looking at the stacking rules for multipliers (p. 12), we can find some indications of what it probably should be. Basically, when stacking two multipliers, they are effectively converted into additive bonuses first, with a bonus equal to the difference between the base value with the single multiplier, and just the base value. From this, it is reasonable to conclude that the stacking here would work the same, but only the multiplier need be converted, since the other is already additive. Thus, using chainmail barding as an example, the calculation would go as follows. Note that the cat is a Large non-Humanoid, so the cost to make it barding is a quadrupling, not doubling (p. 153). Base price for Medium Humanoid chainmail is 150gp (p. 151). Going from Medium Humanoid armor to Large non-Humanoid barding is a quadrupling, which would make it 600gp, a 450gp increase, so the switch to large barding adds +450gp to the price. Going from regular armor to masterwork armor is a +150gp increase (p. 153). All of these increases stack, so your total price is 150+450+150gp, or 750gp.
