You can make report who will work in the following way:
-You will use Standard Cost on Item with the same No. as No. in BOM Component
-This Standard cost will be multiply with value in Quantity per in BOM Component for this No.
-Sum of this results, you must tu update on Standard Cost field for item code same as Parent Item No. in BOM Component
This is a brief description of, but you must to write some code about this.