According to James Simons, "The average annual income of leading research mathematicians (those, say, with at least three articles in the Annals of Mathematics) is about 10,000,000 USD" ;]
Edit: it just occurred to me that, since we are talking about "average" and not "median", this may as well be true, if a handful of mathematicians make a gazillion dollars a year. Very senior faculty members in the top research universities in the US are likely to make only $200-500k per year.