The only cost for maintaining a Kryptium betting house is just the blockchain network fees for publishing and updating event data on the blockchain (a few cents per transaction).
To make this project successful you should somehow make an off chain solution to public odds and events. Also should be an off chain platform to make previous agreement. And only then if both side got a consensus do the on chain contract. Because to run a sportsbook "house" you should constantly track markets and adjust lines "odds". Without that any smart player will rip off any house. If every odds adjustment will cost you on chain fees you can't effectively run the house (the biggest market and lower fees the more frequent line adjustments happen "up to 70 changes per minute at close lines"). It will just cost you a lot to run a house. It's a good idea but it need a lot of improvements to be useful.
It seems you are missing an important point here. Kryptium betting houses do not require from their owners to be market makers. A Kryptium betting house is just a smart contract that registers and settles bets using event data from a specific oracle smart contract. The platform supports peer-to-peer betting, so its actually the users that decide the odds, not the house. Kryptium betting houses can make money (if they wish so) by applying a commission on winnings. In fact, thats one of the big advantages of Kryptium betting houses: their owners dont have to worry about odds.