I stumbled across this blog when doing some background calculations for work the other day, it has a post on Warship Cost Estimates.  He’s done a lot of parsing, of a lot of sources to come up with these numbers.  It’s unlikely that these numbers are spot on (there is no longer one number anyway given all the variables) but they seem reasonably consistent .

The Blog has a bunch of interesting modern Naval commentary as well, if you’re interested its worth a look.