That's almost the same as what I was referring to, only these must be hand-turned vs foot-actuated. I think the ones I'm referring to are called something other than "leveling casters," though. I can't seem to find my info on them. A lot of woodworkers swear by them. - And yeah, $160 each sounds about right, which is why I haven't tried them !
There's also the kind of mobile base made by Shop Fox, which has hand-cranked stops instead of foot-actuated. That's more work, but has the same advantage that you can still quickly get rock-solid support on a non-level floor.