A Grok phone would be cheap to develop, would generate lots of data for his AI, and would fit with his strategy at X (everything app). It's not that far fetched.

It might be cheap or expensive, depending on all of the details.

First "Apple" phone and Apple watch were very cheap.

https://en.wikipedia.org/wiki/Motorola_ROKR#E1

https://www.macrumors.com/2014/12/11/1995-apple-watch/