As an ASuW missile the Penguin is an advance onGood post. I've made that point about the Penguin before too. It seems NZs offensive weapons capabilities as outlined above (Penguin, Mk82) are so tactically limited as to be useless, which begs the question, why bother acquiring them (Penguin) or retaining them (82's). I guess with the 82 it keeps the armourers skills up. AFAIK, we have sold the Mavericks to Peru, as they no longer fit with our new Seasprites.
Replacing the Mavericks with the Penguins seemed like a simple replacing X with Y transaction. Basically because that was what the new sprites were wired for. On paper we have acquired a bigger stick with more range and bang, but not really gained any new capability, and if anything, lost a tactical CAS capability.
Wikipedia gives $22000 (?USD) for JDAM tailkits. This is probably no longer accurate, but my guess is that they are still way cheaper than any other PGM.
Regarding X v Y replacement generally X will always be a generation ahead of Y because it's technology is far more modern. Hence X theoretically offers greater capabilities - more bang for buck so to speak. Don't forget with the new Sprites we got a steal