Most motorized micrometers cost upwards of $700 per motor. While these are quite high quality and perhaps not overpriced given the production quality, for many people, they are over spec'ed and inaccessible. This is a low cost version of commercially available micrometer actuators that uses a 2 phase bipolar stepper motor allowing the micrometer to be controlled with readily available CNC control boards and software such as Marlin.
Pairing these actuators with linear motion stage, a CNC machine with ~5um positional accuracy can be made for low cost.