Shipping by rail adds something like $15 bucks a barrel to the cost.
The oil they ships by rail is discounted at the source so that the landed price at the refinery is the same or less as buying by ship.
There is also probably a higher cost to unloading a trainload of tanker cars than there is offloading a supertanker at your dock. Each tanker needs to be hooked up individually to the pipe and then unhooked when it drains out. With a tanker you many only hook up once or twice. Less labor involved, is less cost to the refinery.
“Shipping by rail adds something like $15 bucks a barrel to the cost.”
Thus enriching the obama supporters who own rail lines.