Digiday: For Slate, getting readers to pay for content was going back to the future. Back in 1998, it was one of the first sites to try a paywall, which quickly failed. Sixteen years later, the politics and culture site introduced Slate Plus, a membership model that kept the site free but offered its most loyal readers additional benefits for $5 a month or $50 a year. A year in, the numbers are solid if unspectacular: Slate said it has gotten more than 9,000 members, which, it said, has exceeded expectations. Still, the numbers aren’t eye-opening, representing an annual revenue intake of about $500,000.