The Australian government, like most modern governments, has figured out that it can make a ton of money issuing coins and selling them to collectors and investors. This 'kookaburra' series of silver coins is one example.
Kookaburra coinage is bullion coinage. That is, kookaburra silver coins are made of pure silver and are sold to people who want to invest in silver. Each coin features an image of the famous kookaburra bird, and these images change from year to year. The denomination and size of silver kookaburras vary from 1 dollar (1 troy ounce silver) to $150 (32 troy ounces silver).
When the government sells coins like this, they usually come packaged in fancy holders with enticing glossy literature. They sell at high premiums, which the government craftily pockets. As soon as you own one, however, its value becomes bullion value. This is true in all cases except when the government intentionally limits production to drive prices upward.
Bullion Value - Just about all kookaburra coins are worth their weight in silver (read further for coins that are worth more than silver). To find the silver value, multiply the silver content by the current price of silver. For instance, if you have a 2 dollar kookaburra with 2.01 troy ounces of silver, and if silver is selling for $17.50 US dollars per troy ounce (look it up at kitco.com), the value of your coin is 2.01 x 17.50 = $35 US dollars.
More than bullion value - You will need to get a coin catalog to find kookaburras worth more than bullion value. Most of the high-value issues are proofs (coins made especially for collectors) and some of them carry small marks such as an American eagle or bust of King George V. Listing individual dates for intentionally limited-mintage coins is beyond the scope of this web site. (Not only that, we abhor the practice of limiting mintage to drive up prices!)