The price on btc-e is very frequently a few dollars less than the other exchanges.  Even taking into account deposit and transaction fees, the price difference is often more than the charges.

Right now mtgox is $116 and btc-e is $109 = $7
Charges/transaction fees 3% of $109= $3.27
Profit $7 - $3.27 = $3.73 / unit

There are other factors to take into consideration, such as the risk that the market price might have changed while waiting for the transfer on the other exchange.  This particular risk could be mitigated if you could convince someone on the selling exchange to loan you the coins.  Also, you might have to wait 5 minutes to execute your order on mtgox, which is more risk...