I enjoyed the interview of Pippin Williamson on a recent “How I Built It” podcast. He talks about resurrecting Restrict Content Pro and his thoughts about being in the WordPress product space.
Also if you haven't seen it already I highly recommend reading Pippin's “2016 in Review” blog post. I always enjoy these a great deal – Pippin shares revenue numbers, challenges, and insights. This is a good look into one of the more popular WordPress plugin companies, and to a degree is a representation of the overall state and trends (like automatic renewals and pricing adjustments) of the WordPress plugin economy in my opinion.