As Ashland said above Kids Sail Free is one of the best deals Royal has (some might say one of the only true deals out there). You do have to make sure you are comparing TOTAL occupancy and correct room category.
Two recent success stories!
My family did a British Isles cruise this past summer, that was originally supposed to be a Baltic cruise in 2020. After many changes due to Covid and then Putin, we finally had a cruise we were going to go on, and we noticed there was a Kids Sail Free promotion going on. Even though they say “new bookings only” they applied it to the cruise, and it dropped our total by over $1500.
A similar thing happened with the cruise we will be taking this March from Barbados. We were Originally scheduled for one cruise, which Royal canceled. They emailed saying we could reschedule to certain other cruises with price guaranteed, I called with the new sailing we wanted. The woman on the phone said “by the way, there is a Kids Sail Free promotion” and added it. The original price for my wife and I remained the same, even though the new cruise was around $400 more per person, and my kid’s entire charge (minus taxes and port fees) was gone, a savings of around $900.