▁the ▁problem ▁which ▁classical ▁political ▁economy ▁failed ▁to ▁solve . ▁ ▁The ▁production ▁price ▁is ▁the ▁price ▁at ▁which ▁output ▁would ▁have ▁to ▁sell , ▁in ▁order ▁to ▁realize ▁the ▁average , ▁normal ▁rate ▁of ▁profit ▁on ▁the ▁capital ▁inv ested ▁in ▁producing ▁that ▁output . ▁That ▁is ▁largely ▁a ▁matter ▁of ▁cost - pr ices , ▁profit ▁marg ins ▁and ▁sales ▁turn over . ▁If ▁we ▁find ▁that ▁the ▁distribution ▁of ▁sale - pr ices ▁for ▁a ▁given ▁type ▁of ▁comm od ity ▁converges ▁on ▁a ▁particular ▁normal ▁price - level , ▁then , ▁Marx ▁arg ues , ▁the ▁real ▁reason ▁is , ▁that ▁only ▁at ▁that ▁price - level ▁the ▁comm od ity ▁can ▁be ▁supplied ▁at ▁an ▁acceptable ▁or ▁normal ▁profit . ▁ ▁In ▁pre - cap ital ist ▁soci eties , ▁where ▁many ▁inputs ▁and ▁outputs ▁often ▁wer en ' t ▁pr iced ▁goods , ▁but ▁allocated ▁" by ▁right " ▁or ▁according ▁to ▁custom , ▁the ▁concept ▁of ▁an ▁average ▁production ▁price ▁would ▁be ▁rather ▁meaning less . ▁Lar ge ▁price ▁differences ▁existed ▁even ▁between ▁towns , ▁provinces ▁and ▁regions , ▁yield ing ▁welcome ▁profit ▁to ▁merchant ▁trad ers . ▁In ▁capital ist ▁society , ▁differences ▁in ▁capital ▁yields ▁are ▁constantly ▁being ▁le ve led ▁out ▁by ▁competition ▁on ▁a ▁larger ▁and ▁larger ▁scale , ▁creating ▁industry ▁norm s ▁for ▁normal ▁returns ▁on ▁invest ments . ▁The ▁cor ollary ▁in ▁capital ist ▁production ▁is ▁the ▁increasing ly ▁free ▁movement ▁( or , ▁at ▁least , ▁mob ility )