Cruise missiles seem to be within the technological reach of a wide range of nations, and we have previously built medium and long-range aircraft capable of getting them within reach of a fair number of targets, so for me the answer is possibly...............whether it is better than SSBNs is another question.
It seems to me that "cheaper" can be defined many ways. It would certainly by MUCH cheaper
financially to abandon a nuclear deterrent altogether. But is this financial benefit worth the
cost in national security? I would think not. Similarly, is the financial benefit of a cruise missile based nuclear deterrent worth the cost in national security and international stability? Cruise missiles have been shown to be (generally) inherently destabilizing.