A good point. Interestingly enough, around a quarter of our testers make > $90k/yr. We don't break it down more than that (and I don't know how active they are in actually testing), but I suspect it was because of interest in the new technology rather than actual desire to make money (even if we do pay well).
With mouse tracking just need to bring them to my web site.
Of course, I understand how better eye tracking is. But I'm not talking about that here.