AppleCare+ cost $29 (£25) for AirPods and AirPods Pro which includes two years of coverage. You can purchase AppleCare+ when you purchase your headphones or within 60 days of your headphone purchase. The warranty covers the headphones and case.
With AppleCare+, you can replace your an AirPod (single) or case up to two times at a discount. It costs $29 to replace an AirPod or case with AppleCare+ compared to $69 or more depending on what you are replacing (see chart for more details).
AppleCare+ does not cover lost or stolen AirPods which you will have to replace under the out-of-warranty price.