I've ordered with WGC and paid via bank to bank transfers many times.
My last order was in the amount of $550.00 U.S, paid via BMO charged a $30.00 process fee. The fee will increase depending on the total amount sent to mainland china.
I've never been dinged with extra charges after the bank wired the funds, nor has WGC ever informed me of "extra" charges on HK's side.
Now one thing that could have arose, my teller whom I've known for years said that funds sent to the wrong Chinese bank can cause extra charges once there. This is due to sending the funds to a incorrect bank within China. The receiving Chinese bank would then charge you extra funds to send it to the correct bank account within mainland china.
When I send money with BMO it arrives at Wacovia Bank China then makes it's way to HK's Bank of commerce in "Kaloon" with no extra charges. This process normaly takes 2-3 days.
Another thing thats is good to know, if your funds are "lost" or if any problems arise with the money wire it will cost you $25.00 to do a trace on your funds, another cost if problems arise with the transfer.....
As far as I know and I do communicate with WGC often, International orders must pay via Bank to bank transfer no exceptions.
I've always been happy with WGC however they will let you sit in the shipping void if problems arise often I need contact them for out of stock issues or back orders.
Hope this helps!