Material cost of Third-Party Order Fulfillment in SAP ByD

In SAP ByD, when the 'Fulfillment' is selected as 'External' in Sales order, then a 3rd party Purchase order would be triggered accordingly.

System will grab the item amount from purchase order as the cost of the sales orders when the delivery is done.

Is it as system standard function?

Can we do any modification so system could get item cost from item standard cost instead of item amount from purchase order?