I pay the yearly subscription for Sync Pro, and I consider it a donation more than anything. I've gotten so many years out of that app, and the developer choosing to repurpose it to Lemmy made my transition here almost seamless from reddit.
There's a one time purchase to remove ads and a subscription for features like machine translation or importing/exporting your communities. It's $17 yearly or $100 lifetime
I'm the same, and had paid for it during the Reddit days of the app. I'm hesitant to pay a subscription this time around, though, since the creator has always left for months and come back with a flurry of updates - which is entirely up to them, but a turn-off for something I'll pay for periodically.
Sync is still my daily driver, and IMO few Lemmy clients come close.