Entry in progress—B.P.
   
Wikiquote: Andrew Carnegie
Andrew Carnegie (25 November 1835 - 11 August 1919) was a Scottish-American businessman, a major philanthropist, and the founder of the Carnegie Steel Company, which later became U.S. Steel.
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Unsources
Watch the costs, and the profits will take care of themselves.
   
American Experience
Andrew Carnegie
One of the captains of industry of 19th century America, Andrew Carnegie helped build the formidable American steel industry, a process that turned a poor young man into one of the richest entrepreneurs of his age. Later in his life, Carnegie sold his steel business and systematically gave his collected fortune away to cultural, educational and scientific institutions for “the improvement of mankind.”
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Carnegie was ruthless in keeping down costs and managed by the motto “watch costs and the profits take care of themselves.”
 
Google Books
Cost Keeping Short Cuts:
Prepared from experiences in many lines of business : illustrated
By Burroughs Adding Machine Company.
Detroit, MI: Burroughs adding machine Co.
1911
Pg. 29:
He knows that profits will take care of themselves when he has taken care of the losses. That is the executive’s part.
   
Google Books
17 May 1913, Domestic Engineering, pg. 179, col. 1:
“Domestic Engineering” says: Take care of the costs and the profits will take care of themselves. Neglect the costs and there will be no profits to take care of you.
 
Google Books
The Business of Trading in Stocks
By John T. Brand
New York, NY: The Magazine of Wall Street
1917
Pg. 109:
Take care of your losses and your profits will take care of themselves.
     
Google Books
1 June 1921, Industrial Management, pg. 19 ad:
Watch the Costs
the Profits Take
Care of Themselves
(L. V. Estes, Incorporated, Industrial Engineers—ed.)
 
Google Books
Management Engineering
Volume 1
1922-1923
Pg. V:
Watch the Costs the Profits Take Care of Themselves