You have paid in full, and the price has gone down. Whether a cruise price drop after final payment is worth anything depends entirely on which line you booked, and the range of answers is wider than most people expect.
Carnival: still open, almost to sailing
Early Saver price protection runs until two business days before departure. If you booked an Early Saver fare and the public price for your exact ship, date and category falls, you can still claim it, and the remedy is onboard credit.
The condition is the fare type. Fares other than Early Saver, such as Super Saver, do not qualify, so the answer depends on what you booked rather than only on when.
Royal Caribbean and Celebrity: an upgrade, not money
After final payment neither line reprices, but both can move you to a higher cabin category when that category is now priced at or below what you paid. It depends on availability, so the sooner you ask, the better your odds.
Princess: no program
Princess retired its Better Than Best Price Guarantee, so new Princess bookings have no price-drop program before or after final payment. If you booked before the retirement, ask Princess or your travel agent whether your booking is still honoured.
Norwegian: it depends
Programs, timing and remedies vary by region, booking channel, fare type and promotion, and Norwegian decides which applies to a given booking. There is no dependable post-final-payment route, though it is not always a flat no.
What to do if you are past the deadline
Three things are still worth checking, in this order:
- Confirm your actual fare type. People often have Early Saver without knowing, and it changes the answer on Carnival entirely.
- Check whether an upgrade is available. Even where cash is off the table, lines will sometimes move you up on a sailing that has not filled.
- Do the cancel-and-rebook arithmetic carefully. It is occasionally worth it, and usually not. Penalties after final payment escalate on a schedule, and you can lose the deposit, the promotion and the cabin for a difference that does not cover them.
The broader point is that the deadline is knowable in advance. Every line's window is published, and on most bookings the valuable period is the months before final payment rather than the weeks after it. That is the period worth watching.
