As a seller of video games for years, I can say right now that it costs either $1.40 or $2.10 at the counter to send a CD, DVD or Blu-Ray disc in a bubble mailer (with the exception of PlayStation 1 games and other cases thicker than a standard DVD cover). It only costs $7.45 if the item is too thick or you are using a mailing box designed for VHS videos (which brings up the cost at the counter to $9.10 if you are buying the boxes on top of the Parcel Post cost).

A movie or a game with no instruction manual always costs $1.40 (in fact, with Blu-Ray cases being smaller and lighter than DVD cases, I haven't actually had a PS3 game go for $2.10 even with the manual included). Of course, this also doesn't cover the cost of the bubble mailer itself.

One thing to note: The $1.65 151x229mm "PB2" bubble mailers that Australia Post stocks do not fit DVDs or Blu-Ray discs, forcing you to pay extra for the larger 215x280mm "PB3" bubble mailers - if you really must buy them at the post office...

You can find 160x230mm (or larger) bubble mailers on eBay which are designed to fit DVDs, and Officeworks also has plastic bubble mailers for $1.05 each which also fit DVDs (they also have red and white PPS bubble mailers which look exactly like the Australia Post ones, avoid these). Additionally, they have a 5-pack of the plastic ones, but for some odd reason they cost slightly more than the loose ones, which drop down to 85c each if you buy 5 or more.