How do sellers ship for so cheap in Australia ???

Anonymous
Not applicable
How do so many Australian sellers ship for so cheap? They sell items that will not fit in a letter (thicker than 20mm) for way cheaper than the cheapest Australia post contract parcel rates.

For example, search ebay for "USB car charger", select "Australia Only" in location, and there are heaps of people selling chargers (including shipping) between $2.50 and $4.00. HOW DO THEY DO IT?? Do they just sent it in a letter, and hope no one checks it is thicker than 20mm? All those items are way thicker than 20mm