One time cost per major version is sustainable, you won't get Silicon Valley rich on it, but you can make a living.

Lifetime licenses only work in the beginning when you have people buying them at regular intervals, at some point the market is saturated and you need to have a subscription model.

Case in point: Unraid. I have two grandfathered "forever" licenses and I'll never need a third.

Yes, the thing with one time purchase is that it should be as it is, right now. Not including updates and support forever.

By this standard, people should feel entitled to get an update on their fridge whenever a new compressor technology is available (or whatever, you get the point).