I have no idea how financially successful they are but the game Dawncaster is great and seems to be faring well. $5 up front, $5 for each expansion (currently

I have no idea how financially successful they are but the game Dawncaster is great and seems to be faring well. $5 up front, $5 for each expansion (currently 2) which add a substantial amount of content each. The devs are active, patching regularly, and planning another content update this year. They just released a free new mode to the game as well. No ads, no microtransactions just a fun and complete game with lots of replay value - I hope they can sustain it over time