The postal cost of items on this site are calculated according to weight.  The weight of each item is listed along side the title, for example, "0.38 Introductory Articles" is stating that the weight of the book is 380gms. Below is a costing for those weights both national and international. 

NATIONAL

Within Austraila

Up to 250gms	$3.70
Over 250gms to 500gms	$4.75
Over 500gms to 1kg	$10.80

INTERNATIONAL

Overseas

Up to 250 gms	$10.00
Over 250 gms to 500 gms	$16.00
Over 500 gms to 750 gms	$23.90
Over 750 gms to 1 kg	$30.85
Over  1 kg to 1.25 kg	$37.80
Over 1.25kg to 1.5 kg	$44.75
Over 1.5kg to 1.75 kg	$51.70
Over 1.75kg to 2.0 kg	$58.50
Every Extra 500gms or part thereof	$8.70

 A handling fee of $5.00 is appplicable to both national and international.