Cracked back glass

You can check the pricing in this link --> iPhone Repair & Service - Apple Support

There are different levels of AppleCare. You get a one year warranty standard on your iPhone, which covers manufacturing defects. The standard one year AppleCare plan however, does NOT cover accidental damage. If your phone is covered by the standard one year plan, you will see what is called Out of Warranty costs associated with the repair you need.

The next level is AppleCare+ which does covers accidental damage and the back glass on an iPhone 13 Pro Max could be be fixed at a greatly reduced cost. You would have had to purchase this plan, within 60 days of original date of purchase of your iPhone.

The final plan is AppleCare+ Theft & Loss, which is like the + plan above, but adds protection against theft and loss.