Weren’t the French selling the RAN diesel-electrics?

Many of the costs aren’t actually fixed. There’s all those extra workers you’ll need to pay, and training will have to be ongoing to account for turnover. Oh, and this is fairly specialized work, meaning if someone decides to specialize in it they may not have a ton of job opportunities outside of Electric Boat and Huntington Ingalls. To even get people to apply you’ll need to increase wages. Even the fixed costs like building some new dry docks and factories could be in the billions. Oh, and you can’t forget everything here has multi-year lead times. Virginia class submarines take 5+ years to build. There are 9 under construction right now per Wikipedia.

This was a lot worse in the Soviet Union. The level of inequality there is hard to comprehend, where your personal essentials such as freedom to move or being able to defend yourself from violence highly depended on your "wealth", that is your standing in the "nomenklatura". Not to even mention actual wealth, like having a car or real estate.