From the text:
Modern man has a deeply rooted belief that objectives should be attained at the lowest cost. Who can quarrel with that? But technical efficiency should never be considered in a vacuum. It does not tell you where to go, but only that you should arrive there (or go part of the way) with the least effort. The great questions are: efficiency for whom and for what? Some goals (destroying other nations in nuclear war, decreasing the living standards of the poverty-stricken in order to benefit the wealthy) one does not wish achieved at all, let alone efficiently. Efficiency, therefore, raises once more the prior question of objectives.
Stress on efficiency assumes agreed-upon objectives. Knowledge of the general welfare, to which the plan is supposed to contribute, turns out to be one of its major assumptions. Without this knowledge, planners would have no legitimacy to tell others what part they should play in this grand scheme.