William Candillon of Start React Native ($5,100/mo) got about 95 sales before he even finished his project this way. He started developing a UI Kit live on YouTube, figuring that even if no one watched, it would still force him to be productive. To his surprise, people in the comments started requesting access to his product. He ended up making $3,000 before launch. The livestreams made him more relatable and gave potential customers a sense of what they would be buying. And they also helped with customer support, because he could point people to relevant videos.