This came to me from the suburb of Payneham in the north-east of Adelaide, Australia. I was surprised to see the $3 stamp, thinking it was a bit much for international mail, but on the Australia Post website I see that International Airmail for letters up to 50g is $2.60. Postcards are $1.70.
By comparison, in Canada the international letter rate is $1.85 CAD (currently $1.93 AUD). In the US the international rate is $1.10 USD (currently $1.19 AUD). Makes Australian postage rates look expensive, but it could be worse. The most expensive international letter rate I know of is Norway: 15kr for a 20g letter, which is equivalent to $2.75 AUD. I guess letter rates in Canada aren't so bad after all. Wish I could say the same for parcel rates.