To aid in getting expired Ethereum Name Service (ENS) domain names into the hands of end users who value them most, the developers of the ENS smart contracts implemented a temporary price premium for expired domains.
After a domain name expires the original registrant has a 90 day grace period in which the name is not available for registration by any other entity. After this period the name is released for registration but with an initial price of $1,000,000.
This price then decreases over a period of 30 days.
Any user can register the domain at the current prevailing price. You can wait in the hope that the price decreases further (to save yourself some money) but the risk is that another entity who values the domain name more highly than yourself will register the domain name before hand.