Rule of thumb is that Tar Sands crude sells at a 20 dollar discount when compared to what deemed “sweet crude”. This number can vary.
There only a few refineries that can deal with this stuff and most are on the Texas Gulf. The Koch brothers own the largest number of these refineries. Canada and Venezuela are the two biggest suppliers of Crude used as feedstock for these refineries.
Here is the thing. This stuff is likely more profitable for the Koch Brothers than is refining sweet crude. While they get the oil at a discount of $20 a barrel give or take , it does not take an extra $20 dollars a barrel to refine the stuff. The Gasoline they make out of this does not sell at a discount.