Wow, that is pricey. $399 is pretty steep, it seems. How has it helped you? And do you think the price was worth it?
Previously I would save notes and never use them. Now my notes are set up in a way that I get more projects done. Having reference material progressively summarized makes collecting ideas and shaping it into a deliverable way easier. Loading context for a project is way easier with a system like this, it makes an interruption much less painful.
The other benefit of taking the course is the forum, plenty of smart people to meet, discuss pkm and other ideas.
It's basically an organization system that serves as an adjunct to "getting things done". GTD's system relies on "filing non-actionable items", but it doesn't really explain how to do that. Traditionally, people would rely on filing cabinets or whatever. BASB relies on evernote to keep basically anything information in there that can quickly be retrieved (becuase you're going to forget years later). And when you later need to the information, you can criss-cross the data for more creative output.
If you are a fan of emacs org-mode (as I am), here's an article that shows how to use it with BASB: https://medium.com/@mwfogleman/implementing-a-second-brain-i...
it goes into the process a little bit, so it can help you decide if the course is worth it for you or not.