“Didn’t we build several destroyers escorts, corvettes and frigates per day during World War II?”
I’ve spent a career building military equipment. If you’re in a war money is no object. The government does not care what something costs, only that it is built quickly and then thrown into combat. So, you can afford to build the specialized equipment to make something which has no other purpose but to efficiently kill the enemy. You can automate huge swaths of the project and produce many of the same item like radar sets, guns, gun loading mechanisms, because it makes economic sense to spend the money to automate. But when you’re not in a war and you’ll build three of something in five years it makes no sense to build specialized machinery. The steel you’ll need will be produced whenever the plant is not otherwise loaded instead of at a priority. Because everything from your logistics to the space you’ll lose is suddenly at a premium then the price of the item goes up.
Several years ago I read that it took five years from procuring the first raw pieces to finish an F-15. But if we were in a war, and not being bombed daily, we’d set up a production line and they’d roll off the assembly line at several copies a day. They’d be much cheaper per plane, but much more expensive as a program. We’d have so many planes that when we left a country it would be cheaper to destroy the jets than to fly them home.
Another huge problem for the American military is that Congress may authorize, say, 150 aircraft to be built over ten years, but they allocate the money one year at a time. Nobody would incur the cost and the risk of automating anything given those conditions. Everything we build today is as if it was a one-off prototype. Yep, that’s expensive.