SEO is a brand marketing tactic, not a direct advertising method.
You do not measure SEO success on revenue generated.
Most businesses have an insufficient SEO budget to achieve success.
Most marketers do not appreciate SEO.
SEO requires strategy otherwise, you will mostly waste time and money.
The fastest way to determine your SEO's ability is to ask to see a website they own or one they've worked on.
SEO is a lot like medicine. You first diagnose why the site isn't ranking, you then prescribe a solution and repeat the treatment as long as it takes to achieve results.
The best way to generate SEO results is to apply the 80/20 approach.
SEO value is often misjudged because of a poor understanding of analytics data.