Subscription models only make sense for an app/service that have recurring costs. In the case of Lemmy apps, the instances are the ones with recurring hosting costs, not the apps.
If an app doesn’t have recurring hosting costs, it only makes sense to have one up front payment and then maybe in app purchases to pay for new features going forward
Doesn’t the Sync Dev (LJDawson) work on Sync fulltime?
Yes And the only reason we had sync for Lemmy so rapidly is that he worked full time on sync for reddit too but he found himself without a stable income from night to day when the API stuff happened.