Well, I do not agree with your characterization of Elon Musk as a scamster. Many years ago on the phone he talked me out of starting a project using his technology because ROI wasn't there yet. As for building a power wall cheaper than a manufacturer can do it, is easy to explain. As a DIY project you do not deal with liability insurance, warranty returns, labor, etc. As the owner of such a project you assume all the risks yourself; bummer when your house burns to the ground and the insurance company won't pay saying the power wall was the issue; a tactic I can almost guarantee they will employ to avoid having to pay until the technology becomes mainstream. Greetings!