alt Hacker NewsEncoders are cheap, even interferometric setup is possible to do at perhaps <$300 if you happen to live near the NeHe rust belt. Actuator backlash and stiction will still be a problem. Good actuators are expensive. Solving backlash is what is nice about this setup.
Sure. For positioning a microscope point to point the backlash wouldn't matter. For an extrusion head it kind of matters. Still not as much as it would with a cutting head, but it is nice to solve it