A land-sea trip isn't cheap. That includes meals on the ship but not on land, and no airfare, excursions, or alcohol. You will spend the least by traveling in the shoulder seasons, May or September. Before leaving home, we had pored over the Princess brochures, picking out excursions. We'd hike a few times and take some wildlife tours.
Excursions can add several thousand dollars to the cost.
You don't have to take any excursions, but on the land portion there's not a lot else to do except self-guided hikes. There's more to do once you get on the ship, like relaxing in the library or in the spa. On our trip, we landed in Fairbanks and the next morning set off for Denali National Park by train. After checking into Denali Princess Wilderness Lodge and having lunch, we were off on a bus tour of the park. In Alaska, you need binoculars to see the beasts.