you forgot to add if an exchange only does say 200btc volume a day thats usually only 1btc in fee's. no VC is going to buy shares in the the ownership of an exchange that only makes 1btc a day. so some exchanges fake volumes, not to make a coin look good. but to grab some VC money
Not only that, the higher the volume, the higher the listing fee they will charge for listing any new token or coin in the exchange.