Hi Pavel, sorry my english.
I try to explain
You create 2 PO, this 2 PO have the item XX
PO 01: Item XX – QTY 05 – $5 Each one = $25
PO 02: Item XX – QTY 05 – $7 Each one = $35
Total Stock of item XX
Stock 10 – cost (5*$5+5*$7=60) – $6 Each One
If you have to change the cost price manually, the POs do not make much sense.
If only it serves to add the stock of the products and not calculate the average cost, of the same product in different purchases, directly some makes the changes in the stock manager.
The idea is that I take the stock and price in the best possible way.
Again Sorry my english
Regards