People will read that headline and come away with the impression that private prisons are making billions. They're expenses are most likely scaling with their revenue.

If your concern is that private prisons exist or that detention is climbing, the dollar figure is secondary to other, better measures. Instead, revenue is (mis)used to give yhe impression that people are getting rich off of this and, while that may be true, the relevant number is the increase in income, not revenue.

In short, NPR isn't above clickbait that's biased towards their audiences.