Paper change is easy: you pull on the last ring of the wire until you can turn it, make 15 revolutions with the wire and all pages including front and back Ti plate are loose. I remember some calculations and if I bought a plate of 2500x1440mm (roughly 100"x57") it would be around 180 euros on materials. Per notebook. But also the laser cutting is pretty expensive. And around €45 per spring/back/wire thing. I made it to fit A5 paper, perforation is a standard Multo perforation, so you could use any paper you like.