We Can't Even Build Small Things

The Advanced SEAL Delivery System is dead after, you guessed it, cost overruns:

A 12-year Navy program to develop six minisubs for commando missions has been canceled after a $446 million investment, leaving the one and only sub at Pearl Harbor with an uncertain future.

With an original estimate that a single sub would cost about $80 million, the price tag for the one vessel that was delivered is $366 million above projections.
...
But after years of battery, noise and propulsion problems, the Pentagon canceled the Northrop Grumman project on April 6 because of performance and reliability concerns, the Navy said.

The numbers are a little skewed in the report, because they credit the whole $446 million to one hull and there's a lot of overhead packed in there. But if Big Navy went ahead and built five more, it's not unreasonable to think the unit cost would be almost, if not more than, double the original $80 million per boat sticker price.