Turns out that many of the pay plans have been fashioned by a NY company called Press+, which was started by entrepreneur Steven Brill (American Lawyer, Court TV) and former WSJ publisher Gordon Crovitz. From AP:
The company says it has launched pay walls for 292 U.S. newspapers. Of course, convincing readers to pay for something that was once free isn't easy. Brill recommends publishers give away enough free page views so that only the heaviest users are asked to pay. "You ease them into the idea that they're going to be asked to pay," Brill says. "It works much better than an abrupt message." Many readers who realize they're about to hit their limit sign up early to save themselves the hassle, he says. On average, a subscriber gained through Press+ pays $6.50 a month, of which Press+ keeps 20 percent.