I noticed Ironwood lacks a cost for a level<11 druid purchasing it from a senior.

Going by what I know, 660 is the cost of a default caster level ironwood, a breastplate weights 30 and we need caster level*5 for +1 enchantment, so boost that by one and you get 720 cost when a +1 breastplate is 1200. What am I missing?