I'm with Bob and Kathy. I have kept track of all expenses on the last 6 of my cruises. The most expensive was the Voyager of the Seas in May, 2003. I paid $1316.00 for the entire cruise (air, cruise, Insurance, upgrade at the pier, stingray city tour and onboard charges. The cheapest was Conquest in November 2004, entire cost (air, cruise, insurance, hotel, t-shirt) $1055.54. My onboard charges were under $100.
I quit doing most shore excursions unless it's something that I absolutely have to do. But I've done most shore tours, and don't need any more souvineers. I usually get a taxi and go do something on my own.