Money isn't real. Yes, allocating funds to this means there is a large swath of the population (with accompanying hard resources) which would work on this when they could arguably be working more productively on something else. But would they be spending their time more productively? Keeping what little remains of our shipbuilding capacity on life support might actually be more productive than the alternatives, given how little of value the US seems to produce when it comes to heavy manufacturing.

"Spending billions" is meaningless concern until you ask the question: what would these people have been doing instead?