I used to pay for a Twitter client, I now pay for a Mastodon client, I contribute to the upkeep of my local friendly Mastodon instance. In all it's in the ballpark of 8EUR/month. There's no world where I would _pay for attention on Twitter_, though.
I am somewhat surprised they didn't just charge for client API access/other bits and pieces (that is, charge the user, not the person who makes the client), and nuke the pay-for-attention/pay-for-flair feature before launch as an obviously terrible idea. I think more people would pay for that. Not many people, but more people, and it would be far less corrosive on the user experience as a whole.