Can't say it is the cheapest around and no idea how good this is.
If you need a few packs, I found there is still stock (not sure for how long).
My total include shipping is $75.
(edit: GST inclusive pricing is added to title, it was left out before)
90% effective according to the TGA. With shipping that works out to be $15 which isn't cheap, but if you can't find them in stores, sure. I bought some from woolies in Sydney's eastern suburbs this morning for the same price. I think they're starting to trickle back into stores from what I've heard.