The US Space Development Agency, focused on missile defense, is working with SpaceX on tracking and communications constellations. But the communications is using laser links for in-space communications. Military Starlink is possible but not proposed yet.
Walter Isaacson, the book's author, gave a long-form interview recently on The Lex Fridman podcast. In case you'd like to form your own opinion about the book's legitimacy, its writing/Musk-supported research is substantially discussed:
>A senior Ukrainian official has accused Elon Musk of “committing evil” after a new biography revealed details about how the business magnate ordered his Starlink satellite communications network to be turned off near the Crimean coast last year to hobble a Ukrainian drone attack on Russian warships.
https://skyandtelescope.org/astronomy-news/the-newest-and-la...
Checkout the latest updates on the new sats, the problem has been fixed.
https://www.pcmag.com/news/no-more-astronomy-photobombs-spac...
This doesn't include launch costs, but starship is supposed to minimize that further. Add in other overhead, then 1 million subscribers is well within spitting distance of break even.
Too bad it ruined the sky for the 15K professional astronomers out there and a big part of the millions of amateurs as well.