Only the Aussies can decide what they really need and will be able to afford. But, I’m reminded of all the years we painted the Rooskies as being 10 feet tall, and they turned out to be only about 5’8”.
In those years,there were few effective means to find out what the Russians were really coming up with,so it made sense to err on the side of caution.These days, American built aircraft & Russian built jets serving with various nations regularly conduct exercises,among other things.