Well as far as I am aware, not much if any of the ad and pricing policies have changed from Sync for Reddit, so it does not make much sense to be all the sudden surprised that Sync for Lemmy continues to be ad-supported. Sync for Lemmy is basically just a faithful port of Sync for Reddit with as few changes as necessary, which AFAIK is exactly what everyone asked for.
ad and pricing policies have changed from Sync for Reddit
The ad-free version of Sync for Reddit (Pro) was around £2 to £5, depending on when you bought it.
There was also a fairly priced lifetime cost for Ultra (around £25). The pricing policy you’re referring to is vastly different from what’s on offer right now. I’m not sure how you’re managing to even compare them.