I mean, there are a lot of people already doing it on Substack.

The common marketing mechanism seems to be to make many of the articles available to non-subscribers (or do this after a time delay), and then they get spread around on social media which acts as promotion for the author.

I wouldn't be surprised if there are some substack newsletters that make that kind of money, especially if people brought a large audience from elsewhere. I doubt many of them are covering local news which is what this sub-thread was about. Personally, I doubt I'd pay $100/year for a newsletter unless it were making me money or really delved into some niche topic of significant interest not well-covered elsewhere. But I'm glad if some people are making a living off it.