Salary and expenditures are related, but not apples-to-apples. The first thing that popped to mind is healthcare. Here's a reference link which mostly overlaps the above graph's timeline:
http://www.healthsystemtracker.org/wp-content/uploads/2014/11/Slide2.png
Next would be administrative costs...we'd have to see if district salaries are counted and averaged into teacher expenditures...since it's all about the children, and what it costs the public (taxes) to pay the teachers (and everyone who supports them within the educational system).
I do see this...
"Work hard to reach your goals" vs. "Wish for it, and the universe will grant it to you"
"Stand out from the crowd" vs. "the tallest blades of grass get mowed down"
"Find the happy medium" vs. "Don't confirm to peer pressure"
We're surrounded by catchphrases of all kinds. Pick your favorite and let it motivate you! Often, answers are not succinct and we have to analyze them after saying "It depends". A strait and narrow path will have danger on both sides, and safety in the middle. The extremes are what we hear most...don't be far left or far right. Well, there is something to learn from each side to further reinforce our individually unique positions. What works for us may not work for others...but we can still preach what we practice.