Traditional SEO retainers usually cap out at 30 percent margins, but...

https://www.save-bookmarks.win/you-re-never-going-to-get-past-30-margins-while-stuck-in-the-client-retainer

Traditional SEO retainers usually cap out at 30 percent margins, but productizing your internal scripts can get you past 70 percent. Treat your agency like a lab to build tools that solve real problems, then sell that software as a scalable product.