How much is the one time payment?

This seems like a bit of a strawman argument. I haven't seen anyone say that explicitly—if they have, it certainly isn't common. I have seen people say they're willing to pay for a "higher quality app," and I can see how you could interpret the implication there being that FOSS apps are shitty in comparison. For me, though, I don't interpret it the same way, and I'd assume positive intent. Some people like Sync better than the other apps and are willing to pay for it. That's it, really.

I might prefer potatoes, but you might hate potatoes.

If we were looking at dishes in a restaurant, I might think one dish is a better value, because I like potatoes. You might think that that dish isn't worth it if you hate potatoes. It doesn't mean that the dish is better or worse, just that we have different preferences.

I don't use sync myself, so I can't speak on what specific aspects other people prefer over the FOSS apps. They might trust the developer more because they've interacted with them for a while, they might like how the UI works with their specific device, or they might even just like the logo. At the end of the day, it doesn't effect me, as I can just keep using jerboa.

Sync for Reddit was a popular app.

After the whole API thing the dev started developing sync for Lemmy.

The open beta was just released.

The free version includes ads.

You can remove ads with a subscription, or with a one time payment of $20.

The Reddit ad free version was like $5, so the price increase pissed some people off.

Also the FOSS or die people got pissed off.

There are many great Lemmy apps, I say just use whatever works best for you.

The Sync for Reddit Dev has released an app for lemmy. People are salty because it's way better than any of the foss apps that are currently out.

Sync for Reddit was a popular-ish third-party Reddit app. The dev has been working on building a version of it for Lemmy, and the surrounding community has been pretty excited for it. Recently, Sync for Lemmy was released, and there's been a lot of fanfare, conversation, etc. In my opinion, it's the most polished Lemmy client by far. Some people are annoyed that the premium features cost significantly more than they did in Sync for Reddit. The dev said it's to offset the smaller user base, which seems reasonable to me, but it's spurred a lot of arguments about the paid model.

The big one is that it introduces ads while Lemmy is an ad-free platform, and the option to pay to remove ads isn’t regionalized, so for some people it’s wildly expensive to buy. There’s also some question about some of the permissions.