Least expensive posting options for magazines using Australia Post
Late last year (September 2019), Australia Post introduced changes to the cost of sending parcels within Australia.
Previously parcel costs were related to weight, but with the new "If It Packs, It Posts" system, you can now send some parcels based on size, which can work out less expensive.
Having sent a few parcels of various sizes since the change, here are my suggestions on how to send out magazines as cheaply as possible.
Magazines under 500g:
Most magazines under 500g are small enough to go as a large letter. Australia Post offer prepaid envelopes that can be used to send "documents" up to 500g and a maximum thickness of 20mm and these come in two sizes suitable for magazines -- C4 (324 x 229mm) for $4.80, and B4 (353 x 250mm) for $5.80 -- but these don't include tracking which is a requirement for PayPal seller protection and good practice.
Instead, I've been using the prepaid domestic letter with tracking C4 (324 x 229) envelopes which are $5.95 and can be used to send up to 500g and a maximum thickness of 20mm. These are made of cardboard and can't easily be folded, which makes them a great way to send magazines without the need for any extra protection.
One or more magazines over 500g and under 5kg:
Small (355 x 225mm) prepaid satchels are available for only $9.20 that can be used for up to 5kg, but these are generally too small for most magazines.
The next prepaid parcel size up is medium (390 x 270mm) which is $12.45 and a better size for sending multiple magazines, but there is another option that might save you a couple of dollars for some shipments.
There is other packaging that you can buy from Australia Post that can be sent under the small "If It Packs, It Posts" rate of $8.95. The largest is a Tough Bag Small which is 261 x 369 and costs $1.50, a total of $10.45. I've used these to send 3 large magazines already, and there was room for more.
There are also some savings when using larger tough bags, as they are generally a similar size to the larger prepaid satchels but fall into a lower postage price category.