There's an argument to be had whether it makes sense for Twitter to have a free API tier. I personally think that it's obvious it should:
- A lot of Twitter content/engagement is created by bots, and people quote-tweeting said bots. Fun bots are actually probably the biggest thing I miss after having moved to Mastodon (fortunately, the all-important Samuel Pepys bot has come across).
- Use of paid-only APIs virtually always stagnates. If there's a free tier, hobbyists and students can do interesting things with them, and this drives innovation. Most of Twitter's important features (retweets, quote tweets, hashtags, etc etc) ultimately originated in third party clients, not from Twitter itself.
- A free API makes it less frictionful for companies to try twitter out for things. If you want to maybe try showing your website status automatically or auto-track customer tweets at you in your support system or whatever, it's easier if you just hook up the app vs if you have to fill out a purchase order for the API access first.
However, whatever about whether a free API is a good idea, it is clearly a _terrible_ idea to kill it on a week's notice. Even for users who _want_ to pay, with only a week's notice many will never hear about it, if their organisation is remotely bureaucratic it's probably not long enough to get the purchase order approved, etc. There's just no possible reasoning to do it this quickly.