What is the best way to post small packages (ie. nail polish/cosmetics) to your buyers within australia?

[cazcaz76]

I've posted similar sized packages with auspost, and they charge me $6.60. But I see some people selling similar items and they're charging less for postage. Is there a cheaper way of sending these small items? How should I package these items and what sort of parcels should I be buying? Do I buy them from auspost or somewhere else? Any advice would be much appreciated!!