… is from page 118 of Robert Higgs’s brilliant 1971 book, The Transformation of the American Economy: 1865-1914  (original emphasis):
Of course, with many employers, each attempting to maximize wealth, competition for workers would soon force the wage up to a level at which it equalled the actual value of the worker’s labor services to the firm. Not every employer must be a wealth maximizer to obtain this result, however. In principle, just one would be enough, for it would pay him to outbid other (discriminating) employers for labor and to expand his business as long as he could continue to obtain workers at less than the going rate…. The evidence is quite convincing that at least some employers in the post-Civil War era strongly preferred wealth to the pleasures of discrimination.