John in NM
Still not cheap, but here's another source that seems cheaper. I would imagine that metal polishing suppliers are cheaper still but that you have to buy a large quantity. I bet the green chrome is cheap due to being used more as a pigment than an abrasive - much bigger market for pigments.

I don't use it on strops, I used to use it polishing rocks. I don't recall CrOx being used much for that, perhaps it is less effective in that regard. I always suspected that a large part of polishing minerals was a chemical action between the polish and the crystal - that was particularly noticeable polishing quartz with Cerium oxide in the surface effects you could see. Alumina generally won't polish quartz either, in spite of being much harder.