A good site I've often checked is this one w1a98k5:
http://www.australian-threepence.co...n-values.htmTells you price of silver in each Aussie coin. So, per coin, each of your 50 cent pieces has $12.23 US in silver content. For your 3000 coins that's nearly $37,000! or 1025 ounces... Or a whooping 1500 bucks if you used them as 50 cent pieces over here.
... or, I've on many occasion gotten these as 20 cent pieces in my change. So you could prolly spend them as 20 cent pieces for a whooping 600 bucks! (I think you're better off with silver price ;))