The handful of smaller exchanges that support Bitcoin Cash gave everyone who had Bitcoins on their exchanges at the time of the fork an equal balance in Bitcoin

The handful of smaller exchanges that support Bitcoin Cash gave everyone who had Bitcoins on their exchanges at the time of the fork an equal balance in Bitcoin Cash, and it's that relatively small amount of on-exchange BCH that people have been trading. (I think one exchange allowed trading before the fork even happened, and just required people to have both BCH and BTC in order to make withdrawals before the fork.) Actual on-chain Bitcoin Cash cannot be sold right now as it can't be deposited in any of the exchanges, and buying it is iffy too due to some of them not allowing withdrawals either. The price of Bittrex BCH has also generally been about 40-50% higher than BCH on the other exchanges for some reason.