1 hour a month for free, $6.99/month for 24 hours of audio for the whole month. The app concept and implementation are great, but the limit is too low to be useful and even the paid amount is not enough. I suppose it's not expensive in the US, but can be prohibitive in other areas.

Best text to speech addon, among the 5 of them I tried today. The voice sounds natural. It has a simple and pretty GUI and gives reading speed control.
One good feature would be the ability to jump into different sections of a page.
Edit: It has a very short time limit of free use. It is OK, but it should have been indicated in the store page.

Works ok, but sadly desirable functionality is by paid monthly subscription...