Traditional retainers stall at 30% margins because of the manual work required...

https://bizzmarkblog.com/what-mistakes-do-agencies-make-when-they-try-to-ship-software/

Traditional retainers stall at 30% margins because of the manual work required to deliver results. If you turn your best processes into internal software, you can easily reach 70% margins. Treat your agency like a lab and start scaling your own products.