I just came back from a cruise and I tell you, these photos sell like hot cakes. After dinner, lots of passengers go down photo shopping..
They are priced USD20-30 per photo, but you can buy a cabin package.. USD399.. you get every photo taken of you and your family (within the cabin) including a digital copy ! (If you buy only one photo, no digital). Some will say, its a rip off.. but consider this, there's around 20+ photographers on the boat, there's photographers on the deck, on the beach, at the pool, at your dinner table, etc. Its like hiring a professional photographer (They shoot quite well)
Of course you can spend your whole holiday shooting photos of your family yourself, risking your iphone at the beach, and at the end of the day... get no photos of yourself and not enjoying your holiday
And yes, they don't force you to buy the photos, if anything they dun even push it to you (like how some attractions do...) the photoshop is on the lowest floor, very hidden.. And if you really wanna shoot your own photos - they sell nikon/canons dslr, point and shoots.. and the Leica M9 + 50cron too...
[I shot lots of photos of my family on the trip myself, and did buy the family portrait shot at the dinner table still]