I disagree. It may be true in some cases and currency, especially in the FOREX market, but it's not true with bitcoin. Unless you have really huuuuuuuge amounts in many brokers.
Cause you can't transfer funds from an exchange to another, it takes too much time! Depending on number of confirmations needed it can take up to an hour to make the transfer! So hard to do any arbitrage...
And you have to see a gap of prices big enough to absorb the fees, you usually have a 0.2% fee that woud'll have to pay twice. Considering the current price of 450$ (more or less) it means you have to ensure at least a 2$ difference ONLY TO BE EVEN!
Arbitrage is for huge amounts, dealt by robots in an automatic and fast way.
At least that's my opinion