How much did these submarines cost?

The numbers vary. The typical cost for boats from Portsmouth or Mare Island during WW2 is generally quoted at $5 million. The first contract for the boats from Manitowoc was for about $3 million and the second was for $3.2 million per boat, plus incentives for early completion.That doesn’t necessarily mean that the boats built in the civilian yards are that much less expensive. It seems unlikely that the accounting is consistent. For example, did the private yards include the costs for the propellers, engines and batteries, which the shipyards didn’t actually build? It seems likely that Navy yards included all costs while the contracts with the private yards may have only included the hull, wiring, piping, and installation of the engines and other large items.

These prices are in 1940s dollars. $5 million in 1943 would be the equivalent of over $112 million today.