Link to a New York Times review of American Colossus by reviewer John Steele Gordon

In his book American Colossus: The Triumph of Capitalism 1865-1900, H. W. Brands writes this, quoting from his earlier book Masters of Enterprise: Giants of American Business from John Jacob Astor and J.P. Morgan to Bill Gates and Oprah Winfrey(p. 59) and from Joseph Frazier Wall's Andrew Carnegie(p. 337):

Carnegie obsessed over cost because it was the one part of his business he could control. “Carnegie never wanted to know the profits,” an associate said. “He always wanted to know the cost.” Carnegie himself explained: “Show me your cost sheets. It is more interesting to know how well and how cheaply you have done this thing than how much money you have made, because the one is a temporary result, due possibly to special conditions of trade, but the other means a permanency that will go on with the works as long as they last.” (p. 93)