While this can be an incentive for some to book I don't consider it a "Sale".
A reduced deposit has never been an incentive for me to book a cruise.
A sale is a significant reduction in the already discounted price. A 1/2 off the brochure price, or "2 for 1" sales are definitely not sales but the standard price of the cruise. Something below the 1/2 off of brochure price may be considered a sale.