actually, out of curiosity, there is nothing grammatically or idiomatically incorrect with the terms "buy and sell". this is because the expression is a hendiadys.
another example:
Mr DMJ Bennett QC: "If one takes the classic hendiadys, talking of a cup of tea, that it is nice and hot, meaning, of course, not that it is nice and that it is hot, but that it is of a particularly desirable temperature; it is nicely hot, if one likes. If one changes the word “nice” to “strong” so one does not have a recognised phrase “strong and hot”, then one would not say the characteristics of the original composite phrase apply to the new one."