Thank you for the info. I am going to try to add a 4th to my already booked 3 person reservation and I was worried the entire thing would get repriced because now guests #1 and #2 fare went up by almost $800 since I booked. So if I'm interpreting correctly, if Guest #3's total fare is showing as $317.61 (assuming port fees are the same) on my invoice, that's what I should expect to pay for Guest #4? I just want to be prepared in case I'm told something different.