I bought a Katsu die-grinder a little while back for circa $30 from one of the Chinese vendors. Haven't done a whole lot of work with it so cannot comment on ultimate durability but so far so good.
Not as sophisticated as Erik's - single speed, no handle, 6mm chuck - but it did come with a variety of burr cutters and abrasive wheels.
Not as sophisticated as Erik's - single speed, no handle, 6mm chuck - but it did come with a variety of burr cutters and abrasive wheels.