The last trip for 7X5 we paid around $11 and the bigger sizes where closer to $18 with the pre-booked portrait before one of the formal night much more expensive but not sure how much. As the prices have slowly gone up we are a bit more selective in what we buy nowadays as I reckon we had in the region of 12/15 taken from arriving on the ship; leaving for excursions and formal nights etc.
Correction for a 7X5 in a folder it was $14.95 just found my stateroom account, it amazing how a few months and the actual price drops !!!