1. Try raising prices by 50% for a month, see if your actual unit sales decrease.
2. Record a video for each chapter and then offer that at a (much) higher price point. $250+ - combine all this together and I bet you could crack $1k/mo.
Thanks for sharing. For technical topics, I think reading is much faster and reliable because readers can skim and also copy code. I'm curious why it might be effective to produce a video and price it higher?