A business has continual costs, which at the minimum may just be the ability to support a single developer's adult life. This app is selling itself once per major version, which judging by some comments here is somewhat unappealing. Many people are justifiably sick of subscription payments. I am also assuming many people would not appreciate e.g. an ad-supported version of something like this app.

So, what does that leave in terms of realistic business options? Are there any examples out there of a software business that succeeds in supporting its own development while helping its customers feel like they are getting their money's worth?