I have a hard time believing that Chrome spends half a billion on advertising each year, given that Google can run its own ads for free. Perhaps that's a estimate for what an equivalent ad campaign would cost a third-party? I agree. A source for that would be useful.

My source on Mozilla financials is the "Mozilla Foundation and Subsidiary: 2016 & 2017 Independent Auditors' Report and Consolidated Financial Statements" - https://assets.mozilla.net/annualreport/2017/mozilla-fdn-201...