“ It is clearly within the special competence of the Commission to appraise the adverse effect on competition that might result from postponing a particular order prohibiting continued violations of the law. Furthermore, the Commission alone is empowered to develop that enforcement policy best calculated to achieve the ends contemplated by Congress and to allocate its available funds and personnel in such a way as to execute its policy efficiently and economically. ”

“ Only the Commission, for example, is competent to make an initial determination as to whether and to what extent there is a relevant 'industry' within which the particular respondent competes and whether or not the nature of that competition is such as to indicate identical treatment of the entire industry by an enforcement agency. ”

“ Thus, the decision as to whether or not an order against one firm to cease and desist from engaging in illegal price discrimination should go into effect before others are similarly prohibited depends on a variety of factors peculiarly within the expert understanding of the Commission. ”