Arbitrage in Crypto

Every time I look at coin market cap and check prices across different exchanges. I think how is it possible to have such an incredible differences in prices across exchanges. I understand to an extent that South Korean markets may be higher because of cross country barriers and not everyone can open an account in South Korean exchanges to be able to buy in the US and sell there.

But sometimes even inside the country, different exchanges have different prices and it seems we should be ready to try and leverage this. If there isn't a bot already doing this.

In the coming month or so, I'll buy Ether from Phoronix, Bitrex, Gemini or some such and try to sell on Gdax/Coinbase because I have seen their prices of ether often little higher than other exchanges. I'll consider it a success if I am able to get 0.5% of the amount I am doing the transaction on, So if I do a transaction of 1000$ and earn 5$ I'll take it as success and would want to repeat it several time overs to see what is the average profit.

Wish me luck !! and Do pour in your thoughts , I am sure I am being increidbly Naive in some ways, may be missing out on transfer fee or time it takes or some such thing.