20% is a huge overestimation. Apple's revenue in 2017 was $239B [2]; Google paid them somewhere between $1B and $9B [1]; 0.5% to 3%.
[1] http://fortune.com/2018/09/29/google-apple-safari-search-eng...
[2] https://www.macrotrends.net/stocks/charts/AAPL/apple/revenue
Interesting is though how the number's been growing over the years, even though the amount of sold devices's been rather stagnant. Google pays a lot per customer, while Apple allows to use DuckDuckGo and others. I wonder how long will Google feel it's that valuable for them (and what a percentage of users'd swich to Google even though other search engine would be default instead)
Apple really has google over a barrel here. You’d have to imagine that google wouldn’t even toy with the thought of not paying the ransom and testing how many people would switch their search engine from the default to google. Also, let’s say DuckDuckGo was the default and users actually liked it and switched their desktop browser search away from google, they’d be really sorry.
edit: This is wrong, I can't find the source for that now but probably it was referring to 20% of services revenue. Its only like 5% of total revenue: http://fortune.com/2018/09/29/google-apple-safari-search-eng...
edit2: This was the source[1], they quoted 24% of services revenue:
[1] https://www.bloomberg.com/opinion/articles/2018-11-02/apple-...