Whatis the best practice in Oneworld and avg product cost?

Hi,

I am using OneWorld for my manufacturing business.

So subsidiary A is manufacturing items and selling them. Lets say $2 per item (manufactured price)

Subsidiary B is retail outlet like a factory outlet and selling items at different rates. Lets say $4 per item bought from sub A.

Right now we have made Subsidiary B a customer of subsidiary A. So subsidiary A is invoicing Sub B.

Sub B is making a vendor bill to receive items in inventory and then selling them to its customers.

My question is, is this the best practice? And since most items are lot numbered inventory items, would it effect average cost in some way? For example, item 1 is manufactured at $2 (system records this as purchase price) in sub A, for sub B, when we make bill and purchase item 1 in Sub B then system records $4 as purchase price for the same item.