Seabourn is disingenuous regarding pricing. I’ve seen this for a few years. I’ve experienced this: book a cruise. Then shortly thereafter, SB promotes, say, a $1000 shipboard credit. But check the price, it has increased by more than $1000. So the “promotion” is a price increase.
A good strategy seems to be to book ASAP after the cruise is released, then watch for a price decrease, then rebook at the lower price. This has sometimes worked for me.
Seabourn sometimes has excellent discounts when booking onboard. Bigger discounts than their advertised policy.