Hi Brandon,
I was unfortunately slugged with the same charge. I contacted DHL customer service to see if I could dispute it and query it and I was given the whole spiel about if a customs officer is sent to the delivery company to check contents of the package then the customer is liable and by importing goods into AU can inflict charges and to contact customs as it is not in DHL's hands and that there;s absolutely peanuts than can be done.
I then read through the customs web site and realised that by purchasing from overseas, yes unfortunately you may be liable for the cost of an inspection fee. (Apparently wooden items are ones that can be inspected often due to them being able to carry bugs etc...)
I then contacted DHL back to pay the $47 and I got a really nice representative who told me she would waive the fee for me as it was the first occurrence and that I wasn't aware.
Maybe try to call them and if your unsuccessful the first time, try again