I do it (http://www.forescoregolfstats.com) for a very simple little web app that I developed a few years ago. I only suggest the one-time fee method if your app requires little maintenance and support. I receive a support request once or twice a month at most and the app runs on lightweight web hosting.

I don't actively push new updates. This month I set aside a few days to rework the interface a bit but other than that the feature base has been pretty static since launch.