> I'm not sure this is a bad thing. If you are a user who actively contributes to the conversation and get's value out of being in that conversation, then it's likely you derive enough value to pay $8. The difference however is that now your contribution is more likely to be seen. You might even engage more now.

I disagree. Diverse input results in better conversations – less of an echo chamber, less black and white thinking, more visibility for other viewpoints, more empathy.

There is diversity among people who want to spend $8/mo on Twitter, but there is far more by definition among all Twitter users. Plus you're likely to discriminate against already marginalised groups in most regions, as marginalised groups (whatever the categorisation) tend to have less disposable income.