I can't find a source for the figure right now, unfortunately. And the whole thing is a guess, since Google doesn't release this information. All it releases is overall sales/marketing spending, which in 2012 was about $6 billion if I understand right (see <http://www.quora.com/How-much-does-Google-spend-on-advertisi...). That includes salaries for the marketing folks, etc, not just direct spending on campaigns.
As I recall, the $1b estimate broke down something like 30% actual spend (primetime TV ads, ads all over the London Tube, etc, etc) and 70% in-kind placement (i.e. "every search you do on Google with another browser shoves an ad for Chrome in your face"). I'll see if I can hunt down where I saw that...
> That's 3 times Mozilla's entire budget
Yep.