Isn't the point of arbitrage to trade on 2 or more exchanges at the same time? So, if you have balances on 2 exchanges, you can do arbitrage without transfers.
No you can't.
Let's say you are scalping XMR on Polo, MintPal, and Bittrex...
Which has been well worth it because the spread is typically about 3% and roundtrip cost is about 0.4%...
And the whole point is to capture that 3% plus any discrepancies between exchanges.
Well, what happens soon...
The exchange where you are doing a lot of selling...
You end up with zero XMR and a lot of BTC...
And the exchange where you are doing a lot of buying...
You end up with a ton of XMR and zero BTC.
So you are always moving around both XMR and BTC between exchanges.
It's better to just call it Market Making and providing liquidity for a fee...
A perfectly honorable profession and a crucial public service to the capital markets.
There are at least 20+ coins and growing where you do this...
And you can always provide liquidity for new listings with a lot of action.
It's Windows 95 in the Crypto Space... this is all gonna get MUCH bigger fast.
Oh, and it helps a lot to be automated and experienced.