There is one other consideration to be thought of, motion sickness. My wife really enjoys the fresh air on the balcony. She feels that it helps her with the motion. Our first cruise we had an inside stateroom and she did not enjoy the cruise as much as she should have. Now that we get the balcony, she can get the fresh air and not feel so much discomfort from the motion.
Also, with the inside stateroom you never know what time it is. When the lights are out you get no moonligh or sunlight, it is just dark.
From our perspective the money is well spent on a balcony room.