Economy theories .. and the poor

Very often you will hear, that capitalism and market system are more efficient than for example centralized systems. - But for whom? 

In economic courses is talked about “Hayek” who writes in his paper "The Use of Knowledge in Society" about “price system”. So the question is, does the price system work for the poor? - If not, than there is something wrong with our economy theories. - We need concepts for all people situations.