'Cold iron' is just iron. It hasn't been worked, heated, cooled, tempered, quenched, etc, into steel. It will probably be the same price as regular weapons, but you'd have to specially commission it, because who would want an iron sword when there are plenty of people making steel?
It might need constant care to keep its edge. It probably won't shatter, because iron is going to be softer- the high-carbon edges of swords are much more likely to chip. But it can get blunt.
I think the trick is, the 300 gp of extra work put into a weapon to make it mastercraft involve repeated heating, cooling, and working it, and carefully monitoring the amount of carbon in it. All metal mastercraft weapons must be steel. Thus, to be enchantable, a metal weapons must be steel, so you'll never find a 'cold iron longsword +1', because it can't exist. You can cast MW or GMW on it, but Craft Magic Arms and Armor has no effect.