You would never know unless you started exploring. Stars have nothing to do with revenue - it's purely a function of how much value you can add to the enterprise. Basically, you have to demonstrate quantitatively that you can charge $X to help them save $Y where Y >> X.

Here's what I would suggest. Reach out to a few people from these organizations and ask them for their general views on your project and what their major pain points are. I'm sure they will be more than happy to talk to you about it if they're indeed already deriving great value from it. Once you have established a good rapport (i.e. warming up the lead), set-up a call with them to pitch your vision for the paid product. A call is crucial because email and text can only communicate so much - you can get a far better idea of their domain and problems through a quick 45 min call. Scheduling this should not be a major problem once you have established a good email channel previously.

If you can get about 8-10 people interested in exploring your paid offering you have something that's promising. After that you can think about scaling the business with self-service etc.