This may not be surprise to many, but the Google pays that amount for keeping the default search engine as google on it's iOS. It is also widely known that the Google pays Mozilla corporation to keep google as default search engine. More on this : Google Pays Apple $1 Billion A Year To Be Default Search Engine on iOS | SiliconANGLE
The Mozilla angle is what keeps Mozilla corp running .. Google quietly funds its biggest competitor in the browser market .. Though at the end its all about dominance. Last year surveys showed Google controlled over 90% of the mobile search market. Also after Chrome became popular Google decided to pull its funding of Mozilla Corp which meant it could no longer continue to function .. but changed its mind and resumed funding.
that would be counter productive, not to mention their popularity would go down severely in open source world. Chrome is anyway a freebie.
