Coverting RMB back to USD

I am looking to extend my tourist visa and to do so would have to transfer money from my home bank account to my Chinese bank account. Do you have any idea how much it would cost to convert about $1,500 USD worth of RMB back into USD once my trip is complete? I am trying to figure out it if it is worthwhile to do this or just to go home and wait until my next trip to China. Does it cost to transfer money to a foreign bank account and how much does it cost to covert RMB to USD usually (how much money do you lose)?