Hi,
this feature was introduced in EHP5 by activating business function LOG_MM_OM_2. As per KBA http://service.sap.com/sap/support/notes/2200601 the standard does not provide the functionality to include the costs of the raw materials into VPRS.
I still try to find a solution for that requirement. So if anybody stumbles across this post and has a solution please share it!
Regards
Patrick