Yep, you've been bamboozled by
ebay's Global Shipping Program. In this case, the seller doesn't even know how much more
ebay will charge in additional shipping from the mailing facility in Kentucky to Australia. The seller may or may nor have charged you shipping from their location to Kentucky (hence the stamp on the shipment cover), but afterwards it's up to
ebay and/or Pitney Powes to estimate other charges to you - express shipping with tracing, customs, service charges, etc.
Unfortunately,
ebay has sold the sellers a sack of lies about the GSP program as well as tricked others into it without letting them know they are even part of it. Some sellers were roped into the program simply by accepting an user agreement update without reading the terms. If the
seller didn't select an international shipping service like USPS or anything else, then the item is automatically enrolled into the GSP program.
As a buyer, you have to determine if a seller is part of the GSP program or not. There should be something in the original listing that indicates the item as part of the GSP program, but again the seller would not know these additional charges, but it was something
ebay added.