That’s a point, too.
This reminds me of a policy I apply to record/mixing projects. You can get a “flat rate”, if you want, but EYE decide when it’s finished. Failing that, you can get an hourly rate where, you sit with me and YOU decide when it’s finished.
I’ve had clients re-write the entire song in the studio … “tick-tock-tick-tock”, and my accountant is happy. 