Yes, MomofKatie is correct. A full week of Leno costs about the same to present as a one hour scripted drama. All they need for Leno to be considered a major success is 5 million people watching (and they're getting that, consistently). Also, keep in mind that Leno runs 46 weeks per year, so between 10 and 20 weeks per year Leno will be new up against reruns on the other channels, so presumably their ratings will be even higher during those weeks.
The reality is that fewer people who count watch television at 10PM and it just wasn't worth the cost of putting scripted programming there.
ABC looks like it might need to get ready to follow-suit, perhaps putting 20/20 or Ted Koppel, or some combination of the two, into primetime (though not necessarily 10PM). While ABC does have some success with scripted dramas, there are signs that there are simply too many to sustain. Castle is struggling, but holding its own, but The Forgotten is tanking, and Eastwick is questionable. (They already run 20/20 on Fridays 10PM.) And a lot of people think that the only reason why Private Practice is doing well is because it is on after Grey's Anatomy.
Take heart, though. Leno's numbers dipped down to 4.5 million this week. That's not good. They're still making more money than they were making with dramas, but not enough to be considered a rousing success. They may stick it out the whole two years, but if this is any indication of what typical audience will be, then we'll see NBC replace Leno at some point. Though it might replace Leno with Dateline. There is still not enough money to be made to justify putting five new hours of scripted programming into those slots.
