So I just took a look because I paid 19cad for the remove ads option which was distinct from "sync ultra".
I think part of what's confusing is there was never previously a sync ultra lifetime price it was always just monthly or yearly. And sync pro was the lifetime price which was also out before ultra was a thing.
If you open the menu, above sync ultra is there a "remove ads" button with a more reasonable (lifetime/onetime) price?