I'm an indie developer, and the $7.99 lifetime license purchase sustains Batteries' development.
What future development needs to be sustained? I developed a similarly-sized app back in the days of Snow Leopard and I’ve not really needed to do much maintenance to keep it going. An hour at most every major OS X version and that was mostly just updating dependencies and recompiling. That’s less time than I spend scrolling HN so I couldn’t justify charging for it.
You’d be surprised!
Thats just my reaction and I wanted to give my feedback.
As a side note: I'm trying to break into the iOS/macOS dev market, do you mind sharing if you make all of your income from indie development? And how long have you been at it?
* abbreviated for clarity