Desire to track cost of machined parts

Summary:

The customer has this goal: Desire to track machined parts in Oracle SCM: OEM parts machined internally - Cost Savings

Current scenario: a basic shaft is bought, a machinist can make it into a finished assembly but this value added is currently not tracked in Oracle.
Goal is to track the value added in Oracle ie $400 to make (say $300 bought item and $100 labor cost) » Clear cost savings
vs
$3000 to buy the finished assembly from OEM for example

Benefits: better cost tracking, transparent cost, overall cost savings to org

Stockroom item is weighted average and would like to track this finished part (machined part) as standard costing