Sales are slowing. Browse the official Ticketmaster website and you will see availability, pretty good availability, for midweek shows in January, and these are not resale inventory. They’re as yet unsold. They will be sold, by show time. But they won’t command the same prices and those weekly grosses will not be $3 million. It behooves “Hamilton” to leave with audiences still wanting more, leaving some room for a return by popular demand.