I've been arbitraging a bit between iPredict and CentreBet. iPredict's prices on Labor tend to be high relative to those at CentreBet. So I'll leave some largeish orders up at iPredict, both near and away from current trading prices. When I accumulate too large a Liberal position (both long Liberal and short Labor), I lay that risk off at CentreBet. So I'm not making pure arbitrage plays because I'm not executing the trades simultaneously - it's more like hedging the risk of a Labor win. But it's not far off from pure arbitrage.
At last update, a Labor win would have me up $43 and Liberal would have me up $370. Both are net figures.
More trading in the interval: a Labor win will now have me exactly flat: gains at CentreBet completely match my losses at iPredict in that case. But if the Liberals win, I'm up $542.
Buying contracts at CentreBet that would pay off at $542 in the event of a Liberal win would cost me $231 at current prices, so I guess that means that straight arbitrage trading has put me up a couple hundred bucks so far.
iPredict traders reading here: please please keep buying Labor from me (selling Liberal to me) at prices far away from what CentreBet charges. I'm rather enjoying this.