Dear Patrick J.
No, it is not transportation that is affecting the price of ND Crude. Remember that oil is a mineral like other hard minerals and has different grades of classes.
Take what you have been told about ND crude (and I don’t know, because I did not look at the gravity) about being “pure” which to me indicates that natural refining took place underground. The other constituent components of crude have been lost - such as the heavies – things that can be turned into motor oil, lubricants, waxes, asphalts, etc.
What may be produced in ND is easy to put into gasoline, there is more to a bbl of crude than just gasoline.
Additionally, the amount of impurities in the mineral greatly affect the price…things like hydrogen sulfide (sulfur).