The iOS and Android app stores likely hold the most examples of high scale one person businesses. Someone already mentioned Apollo. I'd add https://overcast.fm

The iOS and Android app stores likely hold the most examples of high scale one person businesses. Someone already mentioned Apollo. I'd add https://overcast.fm https://overcast.fm and https://david-smith.org https://david-smith.org (maker of many apps, including the wildly successful widgetsmith). There are plenty of other really successful apps that are just one person operations.