Not sure, an open source 3D printer is already cheaper than most laser printers.
Open source 3d printers are great hobbies. I love them, but they're certainly nowhere near production ready.
I think the most sophisticated part of a laser printer is the toner. It has to stick on the drum but also on the paper at the right moment and at the right temperature. And it should stay on the paper for a long time without loosing it's tint.
Maybe they should build an open source laser cutter weak enough to just burn the surface of paper.