Cold Iron Ammunition

[Pinkius]

So, I am making a ranger for the level 12 playtest, and obviously I'm going to want me some (extra) cold iron arrows. It even says, "Weapons made from cold iron are deadly to demons and fey alike." Sounds good.

I'll go out of my way and assume that the 50gp expert cost is applicable to a BUNDLE of arrows, because 50gp a shot is pricey for the 100 gp I have to buy things.

Now... If I use a +3 composite shortbow, and my expert cold iron arrows, my concern is the part of Cold Iron where it says "Weapons and armor made from cold iron can hold one fewer property rune than their iron counterparts." Does my bow still shoot with a +3 attack, 4d6 damage?

If it were a +2 frost composite shortbow, is it +2 attack, 3d6+1d6 damage?
P.S. why would anyone take a +2 weapon with an elemental rune over a +3 weapon, the crit effects aren't THAT good...

TL;DR do cold iron arrows
A) cost 50gp for 10 and
B) lose any bow potency

[Ediwir]

-Ammunitions are made in groups of 10 and use the Light bulk price (p.354, Special Materials, Ammunition)
-Cold Iron Light Bulk Expert items cost 50gp (p.355, Cold Iron)
-The bow is unaffected because it is not made of cold iron itself, the ammunitions are, and the ammunitions are not magical (unless you are trying to enchant them further)
-A +2 frost composite shortbow would trigger elemental weaknesses, dealing an extra 10-15 damage per hit to creatures vulnerable to cold.

Depending on interpretation of weaknesses, and specifically going by mine, a +2 frost shortbow with cold iron arrows would deal the following to a cold-vulnerable demon (say, a Shemhazian):
3d6+15 piercing damage
1d6+15 cold damage
total 4d6+30 damage, or 8d6+1d10+30 and slowed1 on a crit (as the damage is doubled but still only applied once).

A +3 cold iron weapon would just deal 4d6+15 all the time (but crit more often).

[citricking]

Man I read that wrong. I thought it would be 400 gp with 50 for cold iron and 350 for expert, but the 350 from expert is sp and already included in the cost for cold iron. I would have bought some if I realized that :(

[Pinkius]

I suppose it was a bit of a silly worry on my part that cold iron arrows would restrict the enhancement bonus of my bow. Thank you for explaining anyways.

I didn't really consider multiple weaknesses, that is a good point. I didn't think there would be many (any really) demon with double weakness like that; I played in Wrath of the Righteous and they generally had 2-3 varying elemental resistances. A bit meta of me, but food for thought.

[Edge93]

Yeah, that bit on double-proccing weaknesses is right, as clarified by Mark Seifter elsewhere.

And yeah, as said, an elemental bow will hit the elemental weakness of at least a couple monsters in HoU most likely.