Yes, they're real, and they're also doing a job. The 30 percent discount exists so the operator never has to go to 50. They price a slow departure at 30 off, enough people book, and the deeper cut never becomes necessary. Which means the common instinct, seeing 30 percent and waiting for 50, usually backfires.
How the discounting runs. Trips launch at roughly 10 to 15 percent off, which fills the high demand departures like base camp, Circle and South Georgia. Then dynamic pricing goes after the slower sailings with deeper, short-lived cuts.
Deep discounts of 40 to 50 percent do still happen, roughly a couple of times a season across the whole market. Which ship, which date and when are unpredictable, so you can't plan around them. Some operators ran no last minute deals at all last season.
Close to departure you might see another 5 percent, occasionally 10. Not the transformation people are holding out for.
The practical read: if you see 25 to 30 percent on a trip you want, that's the consistent volume discount and it's a good number. Take it.