The real issue is that this is not something "added" to the navy version, is that SAC need to take additional steps to "delete" these features from naval version considering the naval version would be the default. That means you need to R&D two different model, establish different production line, build different parts, etc. All of these cost additional money.
Take the R&D, procurement and manufacture process into consideration, it is hard to say which is cheaper, to produce a slightly less expensive and slightly more kinetic land based model, or just produce a single model in a much larger quantity? I don't know, I don't think anyone on this forum know.