$6.3 billion dollars for a target barge with a 57 mm popgun on the front seems a bit much. (As does a $40 billion dollar Ford-class aircraft carrier and $5~7 billion dollar submarines.)
http://www.gao.gov/new.items/d081061t.pdfDDG 1000 Costs Likely to Exceed Budget
Costs of the DDG 1000 ships are likely to exceed current budgets. If costs grow during lead ship construction due to technology, design, and construction risks, as experience shows is likely, remaining funds may not be sufficient to buy key components and pay for other work not yet under contract.
Despite a significant investment in the lead ships, the remaining budget is likely insufficient to pay for all the effort necessary to make the ships operational.
The Navy estimates a total shipbuilding budget of $6.3 billion for the lead ships. Of this amount, the Navy has approximately $363 million remaining in unobligated funds to cover its outstanding costs and to manage any cost growth for the two lead ships,2 but known obligations for the lead ships, assuming no cost growth during construction, range from $349 million to $852 million (see table 1).
FWIW, that's $6.3 billion dollars
a pop, not $6.3 billion dollars for two.