“This is not necessarily true, however, of measures merely restricting the allowed methods of production, so long as these restrictions affect all potential producers equally and are not used as an indirect way of controlling prices and quantities. Though all such controls of the methods of production impose extra costs (i.e., make it necessary to use more resources to produce a given output), they may be well worth while. To prohibit the use of certain poisonous substances or to require special precautions in their use, to limit working hours or to require certain sanitary arrangements, is fully compatible with the preservation of competition. The only question here is whether in the particular instance the advantages gained are greater than the social costs which they impose. Nor is the preservation of competition incompatible with an extensive system of social services — so long as the organization of these services is not designed in such a way as to make competition ineffective over wide fields.”