Well, let's just do the math: the original pro version has over 100,000 downloads over it's 10 years of life. At $3, that means the dev earn at least $300,000 over 10 years, minus 30% play store fee. Let's say they earn at least $27,000 per year, which is almost twice the minimum wage at the very least.

Now lets do the math for Lemmy version: some metrics say we have 1 million users. Let's assume 10% of them are active users (100,000), and among those active users, lets assume 10% of them (10,000) buy Sync for Lemmy at $3 one time purchase (a very generous estimate). This means the dev will get $27,000 (after 30% cut from play store) from those users, ever. With this amount of money, the dev will need to earn their living somewhere else and abandon their app after a year.