MTICMSTR - MTIC.PROD.RCOST [4] Labor Cost - This level
MTICMSTR - MTIC.PROD.RCOST [10] Rolled up Labor Cost - All Levels
BKICMSTR - BKIC.PROD.AVLAB - Average labor cost

I don't know if this is what you are looking for, but we do a report in Access using WOROUT, WORKORD and WORECV to collect the number of hours for estimated(standard) and actual per work order and average them by part number.  The WOROUT has actual and estimated hours per sequence, and the WORKORD file has actual labor and estimated labor totals.
WORECV filters by receipt date. We can do this by sequence or by total.  I think even if you are only interested in labor dollars you would have to use work order files, and average the labor over a given date range (could be all date ranges).