ations , ▁or ▁in ▁control ▁of ▁how ▁all ▁the ▁price ▁changes ▁will ▁impact ▁on ▁each ▁other . ▁All ▁they ▁can ▁really ▁do ▁to ▁influence ▁the ▁market ▁is ▁to ▁raise ▁or ▁lower ▁their ▁own ▁prices , ▁but ▁even ▁so ▁they ▁can ▁do ▁that ▁only ▁within ▁certain ▁limits . ▁Ord in arily , ▁people ▁have ▁to ▁accept ▁and ▁work ▁with ▁many ▁given ▁cost - price ▁levels ▁and ▁given ▁sale - price ▁levels ▁which ▁they ▁cannot ▁do ▁anything ▁about . ▁If ▁a ▁product ▁cannot ▁be ▁produced ▁at ▁a ▁certain ▁cost , ▁or ▁if ▁it ▁cannot ▁be ▁sold ▁at ▁a ▁certain ▁price - level , ▁it ▁is ▁unlikely ▁that ▁it ▁will ▁be ▁available ▁much ▁at ▁all . ▁ ▁In ▁this ▁way , ▁Marx ▁arg ues , ▁production ▁activities ▁actually ▁become ▁domin ated ▁by ▁the ▁values ▁of ▁the ▁products ▁being ▁produced ▁and ▁ex changed ▁( so - called ▁" market ▁forces "), ▁often ▁quite ▁ir res pective ▁of ▁what ▁human ▁needs ▁might ▁be , ▁because ▁these ▁product - values ▁will ▁determine ▁whether ▁and ▁how ▁it ▁is ▁" e conom ic " ▁or ▁" une conom ic " ▁to ▁produce ▁and ▁trade ▁particular ▁products . ▁ ▁Field ▁of ▁application ▁According ▁to ▁Marx , ▁" e conom ic ▁value " ▁is ▁a ▁purely ▁social ▁category . ▁It ▁is ▁only ▁and ▁exclus ively ▁a ▁characteristic ▁of ▁things ▁which ▁are ▁really ▁produced ▁and ▁reprodu ced ▁by ▁human ▁labour . ▁Thus , ▁things ▁have ▁an ▁" e conom ic ▁value " ▁simply ▁and ▁only ▁because ▁it ▁takes ▁human ▁labour - time ▁to ▁make