$394,49 is the current Spot price for a kilo of Silver - it changes constantly.
See http://www.24hgold.com/english/gold_silver_prices_charts.aspx?money=USD
In reality, it's worth what someone is prepared to pay for it, and because nobody can buy any silver from dealers at the moment, it's worth a lot more.
Looking on ebay, $500 - $600 seems to be about right.
The only reference I can find to a 2007 Australian 1 Dollar coin featuring a Koala is to a pure silver 1 ounce coin with a current value of about $30 AUD. It would probably be suitably packaged in a case.
The approximate value of your coin according to Numismatic News Coin Market Monthly Price Guide for March 2007: 1990 Silver Eagle = $18.00
If you check the back you'll find that you have a halfdollar. There has never been a US-issued Kennedy silver dollar.
Its value tracks the spot price of silver, currently about $13 an ounce.
The silver value of such a bar would be about $2.25 (based on the December 14, 2007 price of silver of $13.98 per troy ounce). An expert would need to see the design and condition of the bar to determine if it had numismatic value above the intrinsic metal value.
The U.S. Silver Eagle is one troy ounce of pure silver. As of 22 January 2013, it's worth $32.
In circulated condition it has no extra value. It's brass, not silver, and was minted in 2007 as part of the Presidential Dollar series. 1789-1797 are the years Washington served as president.
Australian Princess ended in 2007.
As I type this, the spot price of silver is $17.02 so that's about the value of the coin.
Kimi Raikkonen, who win the 2007 Australian Grand Prix
In circulated condition it has no extra value. It's brass, not silver, and was minted in 2007 as part of the Presidential Dollar series. 1789-1797 are the years Washington served as president.
Great Australian Albums - 2007 is rated/received certificates of: Australia:M