I've heard that there exists an old agreement between Germany and Australia, which says that you can send pvstcards for free. I've tried it. I friend sent me a postcard from Melbourne to Germany withvut putting a stamp on it. It arrived with a stamp on it.
postage for a postcard sent from Australia to the U.S. costs AU$1.40.
One Euro.
800 squid
it would be about 40,000,000 miles
USPS.com says it costs 98 cents to send a postcard from the US to Australia.
It did cost $1.10 to mail a postcard in the US in 2003.
It all depends on how much you'r postcard weighs. The more it weighs, the more money it will cost.
about 5 dollars
$.29
50p
Curry
The cost to mail a US postcard 6 inches by 4 1/2 inches is 32 cents as of Feb 2012.