The price is very reasonable if you realize the economy of scale is not there yet. There is only about 100,000 monthly active Lemmy users right now. Even if 1% of those users bought the app at $20, the dev only net ~$14,000 for working on his app full time. The calculus will surely different if Lemmy have 10x more active users which will allow the dev to lower the app pricing while still sustaining himself.
So you're basically saying wait until the lemmy user base grows and see if the dev drops the price. That would lead to a lot of the OG buyers getting angry.
They shouldn't get mad if what they say about gladly supporting the sync developer is true. I meant, isn't it weird to get mad when something you bought actually got lower price a few years in the future? Like buying a game for $60 at launch and then some patient gamers bought them for $10 a few years later. Why angry at that?