Google is known for paying way above market average, but there's also the question of levels. I'd venture to say that most Google engineers I know work two levels below their capability. The concentration of talent is one thing, but the promotion process is so tedious that folks just tend not to go for it. As a result, what you call "average talent" will more than likely get less compensation at Google than they otherwise would. Certainly that was my case, even though money played no part in my decision.