I would also bet that those teachers/professors are working on some lucrative (research) projects or are members of a board of directors, e.g. John L. Hennessy at Google[1].
It's also not really fair to include Hennessy on this list -- he is the president of Stanford, after all. That is a very different job from professor, and pays quite well. According to his wikipedia page, "As Stanford's president, Hennessy earns an annual salary of $566,581."