I've used [versions of] the following graph many times when talking
about the cost of textbooks, as part of building a case for OER.
But I actually think this graph is basically backwards [and
upside-down, inside-out, and otherwise non-optimal].
There is no denying that it does have a certain visceral impact....
...But I think that graph could be improved, actually to show some
measure of the gap between the price of textbooks and what our
— inflation-adjusted — intuition says they should
cost. The measure should be based on comparing what textbooks
cost when a particular person is looking backwards from today to
the cost they remember from when they were a student.