As you can see in the picture ArcGIS Cost Path Analysis produces different results based on chosen direction (blue path direction: start->stop, red path direction: stop->start).
As Cost Path Analysis only works in 8 directions, there are many possible shortest paths in the example above. Some of the shortest paths are located in between the blue and the red path. This got me thinking:
Do you see a possibility to extract the area covered by the many possible shortest paths?
There are large areas of identical costs in this example. Light colors represent low costs, dark colors reperesent high ones.