haha, i don't agree.
It's kind of that, a Seo Expert needs to be the Jack of all trades, including social media optimization and Web Development.
Without the right knowledge, Seo cannot be mastered.
About the earnings, hmmm
and there should've also been an 'effort meter' according to which the Web Developer puts in the most while a Seo or Smo expert just makes use of Automation tools.