The displayed price is $39.57, but when I go to "my basket" GST gets added. Ok, no problems I expect that now. (Though many online shops already add the GST to their display price before you buy it, which is much more transparent, and also required by Australian consumer law - so Merlin should lift their game here.)
By that aside, why is it nearly 12.5%
Goods Total: A$39.53
Delivery Costs: A$9.13
Australia GST: A$4.87
Total (including Savings): A$53.53