I never said they were solely responsible, but it was because of the way they were used that contributed greatly to the differential of cost for such large projects. The premise here is that the cost of building a railroad was cheap and fast in 1862 and that includes all the out lying conditions. At the time they didn't have the demography of today or an established society, and let's not forget law and law enforcement was pretty much nonexistent compared to today's status quo, also it was for the most part raw land owned by the government.