Humans brain are frequently overly aggressive when searching for patterns.
Update: I took 2007 and 2008 out of the long-term average because prices were so much higher in nominal terms than any other year. This flatted the long-term line and shifted the peak into the fall. I also added the following graphs.
This graph shows that some of the price increase is due to weakening of the dollar. Note that WTI Spot is not the price paid in these foreign countries due to variations in grade, contracts, origin, etc.