So far I have not heard of them even being able to reliably produce graphene of any length, and the cost would be VERY high. Look at the cost of carbon fiber, that has a higher likelihood of being incorporated into a filament. Actually a person MIGHT be able to laminate some carbon fiber into say some polycarbonate filament, then extrude it. It would need to be a lager orifice diameter, and bond strength would be the limiting factor. Still that might be the area a person might want to look at.