Dear Kapil,
Labour cost is calculated especially for production. Every production unit involves (a) labour cost (b) Material cost and (c) operational costs. If it is difficult to calculate unit cost then the cost for 100 units or 1000 units is calculated and then unit cost is calculated.
Calculation of labour cost is time taking process. We need to measure the direct and indirect involvement of labour in production of units. While worker may be assigned some machine to work, what about supervisor? He just supervises and does not operate any machine directly. Therefore, apportioning their work is time taking process.
To settle your query, you may do the following calculation:
(total employee cost in FY / total number of tons of steel produced in FY) = labour cost per ton for that FY
Thanks,
Dinesh Divekar