According to the report of Association of American Railroads, US has the best rates in rail freight in the world.

According to the report, based on data from the World Bank and other sources,   U.S. freight rail rates (measured by revenue per ton-mile) are less than half those in major European countries and well below China and Japan as well.

Rail Freight Rates in World, Illustration: AAR

The report also says that the cost of rail freight in USA drops almost by 50% in last 30 years.

Click for the full report of AAR