We have something of a natural experiment here on how much FB traffic is worth to news sites. We'll learn the results in a year if Australia repeals or maintains the law.
We already had a natural experiment, in which Australian publishers were free not to share their content on fb.
I’m not sure how discoverability is going to be effected and that may take a while to see the effects given how locals probably know the locals news sources.
I can't see how you could possible argue they do not provide value to the classic media companies by allowing them to be linked and discussed freely on their feeds.
The market dominance of a couple platforms is exactly the problem here. No organization is in a good bargaining position against them and so soon there will be regulation.
It's already working. Google is busy making deals. Facebook will do the same eventually.
Miraculously, after the Australian government gets involved, Google is now making deals with news media. Facebook will do the same eventually.