Interesting that the regulations they're running up against were built to constrain the railroads, since this looks almost identical to the railroad rebates that Standard Oil and other gilded age trusts used to pump up their monopolies at the expense of smaller competitors and regular people. Basically, if you're a big enough customer, you can play service providers (railroads, power companies, municipal governments, etc.) against each other to get absurdly below-market rates and stick the bill to someone with less bargaining power. The railroad regulations were passed after a series of exposés of Standard Oil and other monopolists that took advantage of secret rebates.

More on Standard Oil, rebates, and the breakup of the trust: https://repository.law.umich.edu/cgi/viewcontent.cgi?referer...

I also recommend Titan, the well-researched John D. Rockefeller, Sr. biography by Ron Chernow.