Rupert Murdoch: iPad subs more profitable than on the Kindle

About 64,000 are subscribing to the newspaper in just the first month; it's also significantly more profitable than the same subscription on the Kindle, he said. Unlike Amazon's insistence on a revenue split, the WSJ keeps all of the nearly $18 it costs for a month of reading.

The number didn't explicitly track those who have passed their free trial periods and are paying for the subscription, although the adoption rate is 20 times higher than just 3,200 in the first week.

Murdoch has been one of the staunchest supporters of the iPad as a means of transitioning from print to digital and during the call said it would "lead a revolution" in how users access all kinds of content, not just text.

Both the WSJ app and magazines like Popular Science have drawn criticism from early iPad owners as their subscription rates are often higher than for the print versions, which carry considerably higher manufacturing costs due to printing presses and distribution. A web-only subscription to the paper costs under $9 per month. However, publishers like Bonnier have admitted that they're partly testing the waters and also see the opportunity to use tablets for handheld features that aren't possible in print, such as video or live Internet components.