It's not actually about the money in that sense. Don't be fooled.

No, they want to kick out third party apps because that cuts costs and the first party app is way better for pushing ads onto users. That's the real investor pitch, they just aren't saying it out loud.

If it was about being profitable, why charge such outrageous prices?

If it's about covering costs created by these apps, why suddenly drop such a huge change on them with an timeframe that can't possibly be met? Why don't they work together with app developers, communicate things well ahead of time and give them some leeway when necessary?

They just want to kill third party apps without outright saying it and the easiest way to do that is to charge costs they can't pay.