The cost to modernize each battleship was estimated by the navy to be about 500 million dollars (back in the early 2000s), a Zumwalt class destroyer costs 3.45 billion (not including the R&D costs). Granted the Zumwalt is the F-35 of the navy, but congress loves blowing money on military equipment.
Same goes for ammunition. A 16 inch shell is about $500, a tomahawk missile nearly 1 million. Missiles certainly have their role, but we have completely eliminated our naval artillery when it is still useful and cost-effective.