Here’s an example:
Let’s say you spent $20,000 on SEO for 6 months, which resulted in the equivalent of $5,000 in monthly traffic value (how much you’d have to pay for the same traffic via PPC).
If you stop investing in SEO, you will continue getting that monthly traffic. Sure, it probably will dwindle if you aren’t focusing on SEO anymore, but the ROI keeps coming.
So after another 6 months – all things the same for this example – your new formula will look like this:
$20,000 SEO investment – $30,000 in monthly traffic value (plus any gains in the first 6 months) = $10,000+ in SEO ROI.
(Note: you don’t have to use est traffic value, you can use lead value, sales, or whatever else you can track.)
Carry that into the future, even with attrition, and you’re getting a better ROI by the month.
That’s why SEO is so powerful and people are willing to invest in it despite how unclear it can be from the outside.
There are clients I’ve worked with that have gotten up to $70k/month in traffic value from SEO while my fee remained the same.