I've always wondered why no Linux app store has risen to prominence? Can one make a living selling their Linux applications to end users?
There are companies that do this- DaVinci Resolve, IntelliJ IDEA, Ardour come to mind.
You can certainly make a living selling a cross platform application that supports Linux, but it's probably quite difficult to make much of a living selling Linux-only applications.
For the seller, being able to sell is one thing, having to run software in a tiny and extremely fragmented market (a large bunch of slightly different distros) is another one. Then osx happened, and the linux desktop never happened.