Home 3D printers can be awesome (I have a side gig involving 3D printing terrain for D&D), but they require a LOT of TLC. I'm sure some of the original hype envisioned them turning into HP LaserJets that everyone could buy and anyone could operate -- and they're nowhere close. I'm not convinced it's impossible to create an automated, reliable, safe 3D printer -- surely Elon's "first principles" thinking could make some progress here -- but nobody's come close yet. So if you give up on the mass market, I would expect a lot of the potential company/stock gains to go away too. Sure, it could be huge for manufacturing. There was an article recently on 3D printing metal parts for the military -- don't need to bring spare parts to the front lines if you can print them on demand there, and all that. But as far as I know, it's always more expensive to 3D print a part than to mass-produce it. So it's great for R&D (way faster than repeated design and casting and testing or whatever), great for low-volume-critical-need type parts like maybe that military scenario, great for customization (3D print a dashboard with your Tesla's name written in, or something)... but that sounds like a lot of niche stuff. I'm sure there will be successful companies there, maybe a military-industrial winner, but not like HP or Tesla where you have to work to think of people to exclude from the potential market.