1925, 1930, 1946 are the 3 KEY Australian Pennies. The 1930 will cost way in excess of 5 figures, 1925 probably $200 - $300, and 1946 may be available for about $100+. I think you need to deal with a specialised Coin Store to acquire them. You could try our member Bigfella, he has a shop in Newcastle, New South Wales.
Email him at: sale@newcastlecoins.com.au
1914 might be fairly readily available, average condition, for $10 and upwards.
1932 average condition or a little better, $5 - $10.
These prices are all AU$, so in US$ they should be a bit lower.
For the 3 KEY coins, you could perhaps settle for "replicas".