The USS OHIO SSBN 726 (lead Trident Submarine) cost $2Billion, new Trident submarines (replacements) are estimated to cost $4Billion. They are rather complex also.
Regards,
HLB
They are also ‘off the shelf’ so some/most of the development and engineering costs are spread over more than one ship. AF1 is a ‘one off’ so it eats all that cost..