As someone who was an initial skeptic when this was first announced, I really appreciate what twitter is trying to do with Blue, especially around direct payments to publishers. Any step to get the internet off of the ad-based data-harvesting revenue model is ultimately better for almost all parties.
Only a small fraction of twitter users will sign up, and the overlap with the kind of users likely to spend money on advertisers products will be big.
I suspect this is true at nearly any price point. Even if it cost $50 per month, the tiny fraction of users who did sign up would be worth more than $50 in monthly ad revenue, since those are the kind of people who will subscribe to other high value services.