Is average pricing what you want?
OpenERP will automatically set the product price in response to each goods receipt movement into the warehouse (a Purchase from a Supplier).
At each goods receipt, the product price is recalculated using the following accounting formula:
NP = (OP * QS + PP * QR) / (QS + QR)
The following notation is used:
NP: New Price,
OP: Old Price,
QS: Quantity actually in Stock,
PP: Price Paid for the quantity received,
QR: Quantity Received.
If the products are managed in this way, OpenERP will open a window that lets you specify the price of the product received at each goods receipt. The purchase price is, by default, set from the purchase order, but you can change the price to add the cost of delivery to the various received products.
Once the receipt has been confirmed, the price is automatically recalculated and entered on the product form.
To congfigure OpenERP to do this:
1) Navigate to Settings --> Configuration --> Purchasing
2) Check the box next to Compute Product cost price based on average cost:
3) On each product you want managed this way, on the Procurements tab, set the Costing Method to Average Price: