The 24 hour package is NOT available in the planner - only on board. It is typically about $3-4 more than the on-board full sailing per day rate. Voom package on board pricing is usually fairly close across the fleet (within $1-2).
For all planner or on board purchases which have one, there's a mandatory 18% grats added.
For the cabin, you can add the $18/day PP grats before the cruise or it will be added automatically on board - those can be removed on board.
CC veterans already now this and newbies will miss this thread after a couple of days. While your cancellation process may have been somewhat rare, pricing error bookings being canceled by RCI is nothing new.
Biker tries to post such that it covers all ships and answer the question that comes from a drive by poster who didn't notice the ship specific question.
As @twangster mentioned that is likely a very rare scenario - especially someone booking their SO in another cabin just to take advantage of their "perk".