That's a misinterpretation of what the blue tick mean. It's to protect the reader from impersonators. That it does help the authors to get followers is an almost unintended side effect.
If you charge for it, you are essentially inverting it purpose, and eventually what will happen is that readers will no longer have that protection, since authors might not pay for it.
Given that, Twitter becomes a less secure place for readers and, if people are smart [1] they will leave it in favor of networks where they can at least trust that what they read came from who they think wrote it.
1: people usually aren't, so I wouldn't be surprised if only a small percentage of people give up on Twitter after this. Still, that's what should happen.
If you charge for it, you are essentially inverting it purpose, and eventually what will happen is that readers will no longer have that protection, since authors might not pay for it.
Given that, Twitter becomes a less secure place for readers and, if people are smart [1] they will leave it in favor of networks where they can at least trust that what they read came from who they think wrote it.
1: people usually aren't, so I wouldn't be surprised if only a small percentage of people give up on Twitter after this. Still, that's what should happen.
Edit: typos