They're only receiving that much because there is a demand for it, if people did not demand these forked currencies then they would be worthless. I'm not sure if Kobayashi sold any BCH but if not we will see the price crash (and probably more significantly so) when he does get around to selling them.
Yeah he did sell a lot of BCH a couple hundred million worth of it. Its mentioned in the first article that exposed this Mt Gox whale.