A big part of the issue is that the oil that is produced in Saskatchewan is not WTI (West Texas Intermediate), but is rather a heavier/more sour oil that generally needs to be upgraded at a upgrader prior to being used to produce traditional oil products like petrol, diesel fuel, etc.  

The charts and website you are referring to use WTI as the reference benchmark.  Obviously in an abundance of the light and sweet WTI grades in the marketplace, the heavier/sour grades of Saskatchewan oil and bitumen have substantially less value.