You need to include the cost of the tenders in your calculations.  Say about equal to a San Antonio @ $1.5 Billion for each 4x Type 212s, to a total of $3.5 Billion, or $875MM per sub.

 

So it would be 24 Virginia's and 16 type 212's with 4 tenders.  Might be better against a low power enemy, much worst against a high end one like China.  A combination of 27 Virginia's and 8 type 212's on 2 tenders sounds better.

You can make an argument for the USN operating SSK's but you run into the fact that an SSN is going to deploy almost an order of magnitude more quickly.  The only thing that makes sense would be forward deploying them and then keeping some in the US for training.

 

The USN with global responsibilities is better served with subs that can quickly strategically deploy around the world.

 

In any case the main reason it will never happen is the moment the USN starts saying it can get the job partially done with SSK's instead of SSN's they will live in mortal terror of Congress determining they don't need as many SSN's as they think they do and make them operate more SSK's instead.  

 

The USN with global responsibilities is better served with subs that can quickly strategically deploy around the world.

 

In any case the main reason it will never happen is the moment the USN starts saying it can get the job partially done with SSK's instead of SSN's they will live in mortal terror of Congress determining they don't need as many SSN's as they think they do and make them operate more SSK's instead.  

 

One size does not fit all.  Clearly there are missions and situations such as the Persian Gulf where a mix of SSNs and SSKs would be superior to SSNs alone.  I'm sure the Navy usually has a few Virginias in relatively close proximity to the Panama Canal, to Japan, in the Med, near Pearl Harbor, as well.

  

 One more idea:  Harpoon missiles have a large warhead and 124km range (perhaps less for sub-launched).  Surely there are a good many targets that are within 100km of shore, like air defense and command/control, even ships in port that could be attacked in the same manner that a  Tomahawk would be used.

 

 I'mm only saying that if capital and operational budgets are at all important, you need a few Prius in your fleet and not just all SUVs.

 

 

 

I'm not saying it's not a good idea nor that I disagree with it.  The point is that politically it's just a non starter in the USN.  The other thing to keep in mind is that there are few scenarios where an SSK might be more useful than an SSN where we won't have allies available with them.

 

As far as the Persian Gulf is concerned the only potential foe now is Iran and frankly we don't need any subs there but if we did I don't think we're concerned over Iran's asw capabilities that using an SSN is a big risk.  Anywhere else in the world we've got allies with very good SSK's which from a USN perspective are already home ported forward.

 

In a perfect world where the political process was rational sure the USN could go to Congress and say long term we think 50 SSN's and 12 SSK's is the force mix we need but that's not reality.  Every new Administration and Congress can and often does affect forces structure and the budget.  What would happen is some in Congress would want to reduce subs,  reduce the number of SSN's, or just increase the number of SSK's because they happen to be built in their region.  From the perspective of the  USN not operating cost effective and useful SSK's is the only rational decision given the actual political process.

 

All this aside the other side of the argument is the strategic mobility of the SSN trumps any cost effective usefulness of SSK's.  Consider a scenario with China with say 12 USN SSK's (with some home ported in Bahrain).  They can't deploy near China anytime soon while SSN's quickly could; moreover, Japan, South Korea, Australia all have excellent SSK's.