User value to companies that serve advertising is based on what companies are willing to pay to serve ads to them. Which is directly tied to the monetary value of that users business to the company buying the advertisement.
Australia is the richest nation (that isn't just a tax dodge) on earth. Sure because the metric used is USD it varies.
I'm going to give you a great grounding example. A typical gardener in this country can take home $80k USD a year. That has to be 4 times or more someone in the USA. I'm not talking a garden contractor in Bellair I'm talking an average Joe.
Google are great at hiding their revenue but I guarantee you that Australia represented a good 20% of the US based revenue. Despite having a population that's only 10% or so.
They would absolutely have their bottom line impacted by withdrawing but they aren't going to. Because of the former sentence.
I don't think the OECD agrees with you there.[0] Ahead of Australia in GDP per capita PPP according to the OECD are: Luxembourg, Ireland, Switzerland, Norway, the United States, Denmark, Iceland, the Netherlands, Austria, Germany, Sweden, and Belgium. Not accounting for PPP the World Bank still puts several countries ahead of Australia.[1] Looking at incomes, Australia is not at the top either.[2] I don't think Australia has an outsized impact on Google compared to the US. If these numbers are anything to go by, then Australia's impact relative to population would actually be smaller.
[0] https://stats.oecd.org/index.aspx?queryid=61433
[1] https://data.worldbank.org/indicator/NY.GDP.PCAP.CD?most_rec...
Source please - otherwise you're just pulling numbers out of thin air.