The way I see it is that a 50g piece of 3D printed PLA could be used to fix a 5kg item that would have otherwise gone to the landfill. I for example have a broken hook for the door tray in my fridge, it's a tiny piece but it being broken rendered the entire 1kg tray useless, it's sitting on top of the fridge waiting for me to buy a 3D printer and fix it.