[random advice from the internet] My intuition is that trying to find new paying users will be a better use of your time than trying to convert free tier users

[random advice from the internet] My intuition is that trying to find new paying users will be a better use of your time than trying to convert free tier users to paid. And it is probably better to extend an existing service in ways that allow paying customers to pay you more money and that attract new paying customers to the solution. At best, a free tier provides an organic path from uncertainty about the service to deciding it is worth paying money for the service to solve whatever problem it solves. In the average case, a lot of free tier use is driven by the psychology of it's-free, and people will quit before they convert even when it is a bit disadvantageous. Good luck.