[经] profit from unequivalent exchange

bù děng jià jiāo huàn lì yì ㄅㄨˋ ㄉㄥˇ ㄐㄧㄚˋ ㄐㄧㄠ ㄏㄨㄢˋ ㄌㄧˋ ㄧˋ