John - Try selling books which are worth more as a bigger profit means you can afford to give a bit on the postage - selling best-sellers and cheap fiction is generally not worth your time listing. For instance I may have only sold 19 books so far this month but its added up to over $800 in sales. Your books average about $4 which means you'd have to sell 200 books to get the same figures. Thats a hell of a lot of photographing, listing and wrapping (and postage).

Obviously with bigger profits you can afford to give postage discounts which makes you more competitive. Buyers know they are getting a bargain when they only pay $6.50 for up to 3kg of books anywhere in Australia and you get more repeat customers.