Make sure you are factoring in taxes and fees charges by the exchanges. Although, if you were to sell on localcoins it would be less expensive to transact in multiple currencies and you save on exchange/broker fees.
But it is basically that easy afaik. Just like any other currency trading (including forex) some currencies are worth more than others at a particular point in time.
You should also ask yourself if your method of transaction is fast enough to do this kind of trade and make the profit you expected
That being said, in the last few weeks people Have been buying XBT with USD and selling XBT for CNY at a premium and then converting that CNY to USD and making a nice chunk of change.
The reason for this is that Chinese citizens have limited access to USD and because most XBT exchanges transact in USD the Chinese can not buy XBT easily. Therefor the chinese pay a premium for their XBT.
What about trying your hand at alt-coin trading on a minimal investment... Say $10 USD. You can learn a lot about these systems of exchange, including where to get XBT cheaper.
XBT = BitCoin