Mozilla CEO gives details on their revenue http://weblogs.mozillazine.org/mitchell/archives/2007/01/the_mozilla_foundation_achievi.html

Almost all of it probably comes from Google. They only spent $8 million and so had about $44 million in the bank. I'm sure they will spend some of that on making it crash less for you, Phillip :)

Judging by FF's growth last year, I'd say they made $80-90 million in 2006