"About half a million households pay a $70 annual fee that includes access to the full database of articles, videos, original documents and access to mobile applications." That's $35 million a year, which is not as good as the best year of the print version (which would have $150 million in sales if I'm figuring correctly), but is still not too shabby.
Books don't need a cadre of software engineers pushing out updates for iOS + every Android device, video transcoding licenses, account servicing, servers, an 800-number staffed with tech support...