Exchange like Betfury cannot set a price except when it is first traded as a base price, this is an old concept when there is a difference price between one exchange and another, the trader automatically adjusts it to arbitrage. Just try to pay attention to the prices on each exchange, if you find a price difference then you can get another advantage of course it needs some consideration and as traders they know what things need attention

I checked Coinmarketcap and the Betfury exchange is not listed there yet so you can monitor it.
The exchange feature on Betfury is more like an internal exchanger rather than a full-fledged DEX. So I wouldn't expect coinmarketcap to add data about Betfury's exchanger as Betfury has no information about the daily trading volume and liquidity for each trading pair. As for arbitrage, I think it's possible, but it's clearly not a good idea. At least, it seems to me that Betfury can ban a user's account if they detect that the user is using the Betfury site for arbitrage instead of gambling.