Bots are probably a very big problem for a small subset of Twitter users, like Musk himself, who is positively swarmed with them. But the median Twitter user is unlikely to care about this problem to the tune of several dollars a month. I get a crypto spam message about once every other day. I wouldn't pay anything to take care of that problem, because it's just not big enough to care about.
I think it's more likely that the real goal of this "Twitter Blue" proposal is to start getting users to pay for bling. Which could work! It certainly works in gaming communities.
Certainly, services for current blue-checks can't be a big part of the plan here, because of:
(1) The Stephen King problem, which is the (correct) observation that people like King are adding far more value to Twitter than they extract from it, and are reasonably not inclined to ante anything up to Musk.
(2) There aren't enough of them to make a dent in Twitter's cash flows.