Needs Only new hotels. A hotel already delivered under this Memory key comes back, whole, when its price per night has moved by at least the Price change threshold (%) since the run that delivered it, for the same stay (same dates, guests, currency and market): previousPrice, priceChange, priceChangePct and priceChangedAt are filled. Charged per hotel that comes back as Price change, on top of the hotel itself, see Pricing; a hotel whose price did not move enough is skipped and costs nothing, and a hotel with no price is never a change. Use fixed dates (for example 2026-12-20): a relative check-in such as 14 days moves the stay at every run, so its prices are learned again instead of compared. The first run after you tick it learns the prices and reports no change. Each search is read to its last page (1,000 hotels per search at most) because any hotel of it can change its price: a run takes longer than with Only new hotels alone, which stops after 20 pages with nothing new. Unticked (default) = the four columns are always null and nothing is charged.