Ask HN: Free vs. fee beta programs

I'm working on a project called Booklaunch.io. Like an About.me for books, authors can create a beautiful page to market their book, collect email registrations and lead readers to purchase links.

http://booklaunch.io

Currently we are beta testing, trying to get a lot of users into the system to see their habits, system use, likes/dislikes.

Authors can log in and build their book pages for free—they pay on launch. Beta testers get 33% off the listed monthly / annual price.

We are trying to validate whether writers would pay for this service. To get more users, we are considering switching to a free beta. How accurate is a beta tester survey after the fact that asks "would you pay for this service?"