>>Also consider they're not buying groceries, paying a mortgage, buying gas for the lawnmower, fuel and insurance for the car, repairs to the garage door, fertilizer and weed killer for the lawn, etc.<<
Right, they're not doing that for themselves, Thomas, because they're living on board. But many of them are supporting whole families at home. As one crew member on my last ship put it (and he was American, BTW), "Some of them are supporting entire villages."
NCL crew members work 10-10 1/2-month contracts, BTW. Or so I'm told by many NCL employees.