X is finally following through on its long-rumored plans to sell old user handles, and some of the most sought-after usernames could fetch millions of dollars. The company shared more details about and opened a waitlist for its "handle marketplace," that will enable paying subscribers to request and buy "inactive" handles.According to the company, X will make two types of "inactive' handles available: "priority" usernames that may include "full names, multi-word phrases, or alphanumeric combinations" and "rare" handles that consist of "short, generic, or culturally significant names." Subscribers to X's Premium+ and Premium Business tiers will eventually be able to request some "priority" handles as part of their subscription. The company says @PizzaEater and @GabrielJones are possible examples of such handles. Notably, this process requires what essentially amounts to an indefinite subscription to X Premium, as the company says it will revoke priority handles if an account's subscription lapses.