Use your savings in the port.
Like most aspects of travel, there are advertising prices – and then the price you actually pay. Apart from being at Disney theme parks (with its incomprehensible price stratification), this is more realistic than nothing on a cruise ship. When booking a cruise, you might read that a week-long sailing in the cold winter north is only about $600 per person, including everything. At bargaining prices, you can book, right? But please stick with it. To maintain this price, this may mean that you won’t order an alcoholic beverage or register for a shore excursion in the indoor cabin.
Even so, cruising doesn't have to cost thousands of dollars per person. There are several smart hackers to cut costs. They may look tiny potatoes, but in fact, once added up, you will put more money back into your bank account. Maybe this can be paid for future tours?