One-shot option seems attractive, but the desktop (MacOS at least) app market is actually so niche that the SAM is somewhere in the low thousands. So, if I would offer a one-time 100$ app, I'd have 100k$ before taxes. And for that revenue, there's developing, marketing, plus support and maintenance. So to match a dev's salary, I'd need to make 2-3 successful apps a year, that I'd also have to maintain for a long time.

I think maybe there's a mid-ground with buy forever, 1 year updates, so people get the product they paid for, and if they want updates or support the development they can re-buy, however I'm yet to hear opinions on this model.