Surplus value is a concept created by Karl Marx in his critique of political economy , where its ultimate '' source '' is unpaid surplus labor performed by the worker for the capitalist , serving as a basis for capital accumulation .
Surplus value is a concept used famously by Karl Marx in his critique of political economy , although he did not invent the concept . 
 Marx argues its ultimate '' source '' is unpaid surplus labor performed by the worker for the capitalist , and the surplus - value is the primary basis for capital accumulation .