Under Prices you will see statistics over the Last purchase price, Average purchase price and Mean price.
Last purchase price is the price entered during registration in the Register Supplier Invoice procedure.
Average purchase price is an average of the prices based on the 10 latest supplier invoices. If you have not activated the setting Create supplier invoice basis during Arrival Reporting? under Accounts Payable under the Purchase tab in the Settings procedure, these statistical prices are created during arrival in the Arrival Reporting procedure.
Mean price is an alternative average purchase price, which can be calculated in the Calculate Mean Price procedure in the Inventory module.