Is this quotation from Robbins?
"so long as the Theory of Value was expounded in terms of costs, it is possible to
regard the subject matter of Economics as something social and collective, and to
discuss price relationships simply as market phenomena. With the realisation that
these market phenomena were, in fact, dependent on the interplay of individual
choice, and that the social phenomena in terms of which there were explained --
costs -- the valuation of alternative opportunities -- this approach becomes less
and less convenient."
Michael Perelman