I think there's a difference between general anonymity and anonymity to those running Twitter. Limited general anonymity can be maintained even under Twitter Blue and therefore the unhinged would not see more detailed information. It's "limited" due to the fact that most governments will have access to the identifying information.I agree that being identified would likely curtail abuse, but on the other hand it makes people targets of the truly unhinged.
I think it would help to make Twitter Blue more used for those who actually post to Twitter. It's a clever way to reduce bots. I am in read-only, so would not have occasion to find it useful, no matter whether it is $1 a month or $20.
In the end, Twitter wants everyone on Twitter Blue, so that we can send and receive money, do basic banking, buys stocks, send and receive monetary tips, etc. Because of this, I doubt that the charge will be very high. Or there may be both a Twitter Blue and Twitter Green.