I don't see why people would pay for this?
I also felt like saying, maybe just for fun, that I feel Twitter was better without the check marks, it felt like everyone was equal, that was nice.
The same logic applies for most managed accounts I think: politicians are basically the same with the exception of 1% who actually run their own accounts (for better or worse). The other 99% are basically just advertising their campaign, whipping votes etc.
Letting Sony or <boring senator number 37> have an account gains twitter nothing really, it's actually costing them advertising probably since such corps can tweet for free. That's my cynical opinion at least.
For people providing actual useful information (I couldn't think of an example but someone else suggested scientists) I think you're right that it's worth more to Twitter to clearly mark them than to the individual themselves. Maybe they can add a free tier for people with .ac emails and accredited media orgs?
At best this seems like a nice way to charge very rich or corporate backed users for the service twitter currently gives them for free...
Basically, it sets up the platform for "All speech is free, but some speech is more free than others."