I think the OP is taking generous liberties in making the comparison. If he is renting a condo on the beach, purchasing food and renting a car, his $4K land vacation includes: cooking his own meals, finding and paying for his own entertainment and probably making their own beds and cleaning up after themselves. There is a big difference between renting an "on your own" condo and going on an "everything is done for you" cruise. The two cannot be compared.
He also has included in his calculations all of his shore excursions. That alone is not included in his land vacation.
(cruzin' solo by design)
Freedom ('09), Imagination ('08), Victory ('08), Destiny ('08), RCCL Navigator ('08), RCCL Majesty ('08), Glory ('07), Liberty ('07), Fantasy ('07), Destiny ('06), NCL PofAm ('05), Fascination ('04), Victory ('04), Fascination ('04), RCCL Voyager ('03), Fantasy ('99)