The business drama behind the New York Times paywall is, at its core, this: can the news organization find new subscription revenue faster than it loses advertising revenue? And, while it has pioneered the paywall, signing up 676,000 subscribers through the end of the first quarter, the announcement that it will offer new, cheaper tiers shows that is not enough paying customers. As its most recent earnings report show, while advertising revenues fell 11.2 percent in the first quarter while circulation revenues, including digital subscriptions, rose only 7 percent—not fast enough to keep up with the changing business model.
The problem, as this chart from Zach Seward at Quartz shows, seems to be that The Times may have signed up most of the people willing to pay at least $180 a year (which is currently its lowest priced digital subscription) for the Times journalism they read.
That means that while digital subscriptions continue to grow, they're not on track to grow explosively from its current level around 700,000 (which, incidentally, is not too much lower than the 1 million-ish print circulation The Times had before the big, bad Internet changed everything).