The photos aren't cheap. I believe an 8 x 10 will run your around $19.00. It may even be slightly higher. I'm sure someone here will know exact amounts. My advice would be to look over your photos every day while they are out on display. The photos will stay up the entire cruise for your viewing pleasure.
We usually go on our last evening and pick and choose the best. They will take more photos of you and your family than you have room in your home. If there's an absolute fantastic photo that you can't live without, purchase it. You can very easily go over board on photo purchases. There will also be key chains, photo albums, frames, etc., available for purchase. This is where the sign and sail card gets dangerous for me. I'll take two of those, four of those.....
Photographers will be out every evening, when you disembark the ship and even on some excursions.
Have a smile ready at all times.