The first time we launched ProdCamp on PH we had no payment system... We got hundreds of signups. But nothing to prove the feedback we were receiving was coming from the audience we were looking to listen to. When we made Prodcamp a paid subscription and promoted it again we got much more qualitative feedback. Only today after two years of development we are ready to relaunch a free plan! But lesson learned! Make sure you listen to people that are ready to pay for your product if you want to use feedback to drive your roadmap.