R12 Inventory Item Master Org Costing vs Child Org Costing

Per MetaLink note 782748.1 - I understand that costing can be controlled at the Item Master Org level or the Child Org level, but not both.

So if you have 1 item Master and 5 Child Orgs, you cannot have some Child Orgs getting their cost from the Item Master Org and other Child Orgs defining their own costs.

However, when I am setting up my Child Orgs, in the Parameters->Costing Information tab, the Costing Org defaults to the Item Master Org and cannot be changed.

So how it is possible to define each Child Org as it's own Costing Org?

I am currently in the setup process for the Orgs, so there are no items defined yet