This is a great idea by Izhar Gafni, from Israel. He is close to producing it for real.
It’s expected to cost a mere $20 and weigh about 20 lbs (9 kg) — that’s 65 percent lighter than an average metal ride. In fact, this bicycle doesn’t use any metal parts at all — the solid tires are made of reconstituted rubber and a car timing belt is used instead of a chain.
I’d buy one just to go back and forth to the store with. It’s also a great idea for kids, because goodness knows I went through 3 bikes as I was growing up.
I sat on cardboard furniture once in a museum and found it surprisingly comfortable. I thought it would be awful and uncomfortable, but it was quite nice!