A Power Adapter Is Not Included
At this point, it should come as absolutely no surprise that Apple isn’t including a power adapter with the AirPods Max, since it’s pretty much eliminated the charging bricks from almost every other product that it sells.
What you will get is a USB-C to Lightning cable, so you’ll need to have a USB-C power adapter to charge your AirPods Max. Of course, since it’s Lightning on the headphone side, you can also use any USB-A to Lightning cable that you already have around, and presumably Apple is banking on the fact that most buyers will already have one or more chargers available, and with 20 hours of battery life you likely won’t need to charge them all that often.