They already have an enterprise tier for people who want to build commercial stuff on top of Twitter, and they already monetize their datasets and have done for years. How do you expect to sign up students/new developers if they have to pay before they figure out how to use the API?
Well they mentioned "basic tier API", so I guess let's wait for the pricing and capabilities, no? My main criticism is they're not being assholes just for charging for an API access to their data.