Why is they claim her to be underpaid?

"Judge Judy," of course, centers on former family court judge Judith Sheindlin (69 years young!) deciding small-claims cases with her trademark brand of common-sense wisdom. And she gets paid very well to do it: As of 2010, Sheindlin was already pulling in a whopping $45 million a year from the show. As ridiculous as that sounds, with these ratings, it's entirely possible she's actually underpaid.

Can somebody tell from what sense that the paragraph claim that she is underpaid?