Richard D. Wolff

I have also thought about this. Capitalists buy labor power for a wage which is paid to the worker after a given amount of labor is performed. The worker is living labor in the productive process and adds value to commodities, goods and services, which are subsequently sold. Capitalists buy labor power at its exchange value (wage) and get its use value (living labor). Since they get the value of the wage back ,plus profit, capitalists are able to make what is called in finance a “spread”. For example, if a worker is paid $15 in wages per hour and produces $20 ,the capitalist gets to keep the 5 dollar profit. This is equivalent to saying, assuming the work day is 8 hours long, 6 hours are paid and 2 are unpaid. This is how Marx proved that even assuming that commodities exchange at their value, exploitation occurs. I hope this helps!