It would have ended up being cheaper by far to upgrade tomcats than to buy new F18's to replace them. Not to mention the F14 is more capable of doing AG roles and about equal at AA roles. On top of that the F14 has a better saftey record than the F18, which should be more important than cost because, after all someone has to be in this thing when it goes into combat.
Give me 24 hours and I'll have sources to back this up.