> Add up all their book fees and speaking fees that they’ll never have to repay back. They can already retire comfortably.

Don't forget their faculty salaries. Duke is a private institution, so we don't have access to his salary, but absolute minimum Ariely makes 400K (and probably way more). You don't leave MIT for a chaired professorship at Duke unless it comes with a very, very hefty salary. 25 years of a salary like that will by itself provide you with a good retirement. You don't need to get the media attention of Ariely to benefit from fraud.