Not all of that revenue is search. When you add consider not all of that revenue is from Search, the cost of compliance (adding more to legal team and the toil of actually negotiating with all the other parties), much less actually paying for the links, they might see it as genuinely not worth it so it might not just be a case of punishment for Australia daring to regulate them. In that case, other search engines that pick up enough market share for the law to apply to them, which will probably much less profitable to begin with, will feel the same way.