SpaceX works because a lot of people want to put satellites in orbit. In a time of unprecedented peace, how many navy ships do we realistically want to be building?
$4.25B/ship is the wrong way to frame it. Think of it as $23B to keep our shipbuilding expertise current, to make sure we have the capability to build navy ships that incorporate a bunch of cutting-edge technologies (some of which have worked out and some of which haven’t, as is the nature of cutting-edge technologies). If a shooting war started to look likely we’d be building a lot more than 3 of them and the unit cost would come way down.
.. It seems you should be able to bring down a 4 billion ship with a swarm of thousand drones for maybe 1 million each for the total cost of 1 billion. Same for aircraft carriers.
.. The lack of a missile defense system on the Zumwalts has more or less made them pointless beyond research/development testbeds.