Marco Arment has been solo building really cool stuff on the internet for years. While he was the CTO of Tumblr, he launched Instapaper in 2008. He left Tumblr in 2010, sold a majority share of Instapaper in 2013, and then turned his focus to Overcast, one of the absolute best apps you can use for tracking and listening to podcasts.
In the course of all of this, Marco has watched the Apple App Store grow and transform from a nascent market for card games and social media apps to one of the biggest platforms for making money on the web. He knows the platform better than most people. He also knows how to make really cool things — all of which he does solo.