My point isn't that Apple doesn't care about the money it makes from the app store, my point is that Apple has a vested monetary interest in keeping developers around going forward. iPhone sales pre-app store were pretty small; the app store drives a lot of their business.

Twitter, on the other hand, has no business interest in developers going forward. It's true they may not have gotten where they are without third party devs, but that need is gone now; they can move forward without them. You may lament that as being cruel in some manner, but that's business my friend. Twitter isn't going to collapse because they cut off third parties.

Just recall the first iPhone: its presentation was met with a lot of scepticism, it was very limited feature wise, it had no apps ecosystem and still was a huge success.