Personally, depending on my mood, if I have the obnoxious "sign in" prompt that medium and others give I'll maybe just not read the blog at all 1 time in 4. I am sure I am not the only one that gets put off by that crap.
If they had a simple sign in/sign up/dismiss prompt I wouldn't avoid it as readily.
Instead they have "pardon the interruption" and "Let's make this official". The "pardon me" politeness doesn't fly, because they recognize it as an interruption. If they are aware, then the polite thing would be to not interrupt.
And let's not make this official.
I don't want to sign up to read an article. I don't want the clap. I don't want to vote. I don't want to share my data. I just want to view the article. Maybe half way through I might even decide that the author has nothing interesting to say. 50% chance I don't want to read the full article.
There's a shifting demographic of medium readers that occurred with the recent introduction of more and more nagging on their site and plenty of blogs that moved away from medium mention it. You might still get your deserved readers if you target social medium experts and marketing managers, so good luck to those who's willing to circleyank with this.
Sure, there's a lot of reasons to prefer your own blog over Medium, if only for the sake of your readers. Earning money for many is not one of them, though.
Jekyll + Github Pages / Netlify / Surge is free with subdomain. Or you could buy .dev (or anything else) for minimal price. Personally i bought 1$ .xyz domain. Its not that “costy”.
It doesn't cost me a lot of money, indeed, and I'm happy to pay the couple of Euro's that it does. GGP suggested that you shouldn't let Medium earn money over your content, though; even if that's something you care about, it's still a better deal than paying for your blog yourself.