Hi RJ
This source shows a variance to the differentials to yours which indicates the WY Sweet to be less than US$3 below WTI.
http://eadiv.state.wy.us/creg/WyInsight.pdf
Elk not needing to pay 3rd party transport costs would give it a small premium ( if the above source is correct) if that is really how it works.
Cheers
Dan
