Great catch, it is the top three players who win. Given ethereum and the gas costs it can't possibly be any cheaper than this without making it centralized (no smart contract, just sending ether to a regular address).

Without a smart contract there are no guarantees you will get your money back if you win your game (thusly you have to build a lot more trust in a centralized game than in a smart contract game).

I'm an ethereum developer so I wouldn't know where to start "[using] STEEM".