Testimony of Jay Gould, May 19, 1887, PRC, 1:588.
For actual costs, Testimony of James W. Davis, June 21, 1887, PRC,3:1087.
The best American bar iron was running between $146 (its peak) a ton in 1865 and $75 in 1870. Pig iron ran between a little under $60 to a little under $40 during this same period. Ties usually ran 25 to 50 cents.
Poor's statistics are often mutually contradictory from table to table, but they are still the best available source for these years.
Adams to S. R. Callaway, Dec. 1, 1884, UP, PO, OC, vol. 24, ser. 2, r. 21.
Adams to Hoyt, Feb. 4, 1885, UP, PO, OC, vol. 27, ser. 2, r. 23.
Adams to F. Ames, April 23, 1885, UP, PO, OC, vol. 28, ser. 2, r. 24.
Grodinsky, Transcontinental Strategy, 164-65.
Adams to G. W. Cushing, July 16, 1889, UP, PO, OC, vol. 48, ser. 2, r. 43.
The literature on this is enormous and starts with Leo Marx's classic, The Machine in the Garden: Technology and the Pastoral Ideal in America (New York: Oxford Univ. Press, 1964).