It doesn't matter whether your office chair is cheap or expensive, the wheels will eventually pick up all sorts of dirt and grime. You can brush a lot of it off, but home and technology blog Apartment Therapy Tech recommends a butter knife for more effective cleaning.
Bust out the butter knife for stuck-on stubborn material. Angle your knife nearly parallel with the wheels, holding it steady, but "slicing" in the same directions as the wheels spin. Spreading onto toast afterward is not recommended.
For additional tips on getting the grime off your task chair's wheels, hit up Apartment Therapy Tech for the full post.
How to Clean Task Chair Caster Wheels for Smooth Rolling [Apartment Therapy Tech]