I suspect that extensions on the App Store that are popular make more money compared to being, well, free on Chrome web store. Or, developers are pricing their extensions to recoup costs on dev program costs.
I'm working on a mobile version of a card game my friend's dad made! In between shifts at the hospital, it's been a great way to take my mind off of everything going on in the world.
It's funny, for someone with a formal computer science education I've never tried making a mobile app before! We don't really expect to make a lot of money off of the app, but we've had a blast going through the whole process.