My goodness do they make it up as they go along 😮

Australia Post own terms and conditions (section 73) outline compensation is for replacement value - nothing about cost value - this is a variable that can never be assumed to be lower than replacement value.

They are leaving themselves wide open for you to send in receipt for purchase of the garment when new.

When I have sought compensation for (signature required) parcels, I have only ever had to provide copy of ebay sale - and emailed in copy of order form.