Activision is completely changing the way it handles Call of Duty DLC starting with Black Ops 4. In the past you basically got a few maps (one of which was usually a remake of an old arena) and a zombie level. If you wanted, you could buy a season pass.
Now, it’s all pass or nothin’. Thankfully the main draw, the zombies content, is sweetening the pot.
Source: Destructoid Call of Duty: Black Ops 4’s Ancient Evil DLC is bonkers, even for zombies