In a log linear Cobb Douglas production function for two inputs labour and capital, which value of labour; the absolute value of labour or labour prices (wages) will give good result if capital used are taken in price values.
A Cobb-Douglas production function typically uses the amount of labor (L) and capital (K).
The Marginal Products of labor and capital can be derived after estimating the Cobb-Douglas production function. Then wage rates (i.e., the Price of Labor Services PL) and something like the rental price of capital can be used to determine if the firm is operating in a least costly manner.