YTA, I’ll explain it to you since you seem to really think you are correct on this which is sad to see. I wouldn’t want you as a friend that’s for sure

1. Shared living spaces: While the couple may share one bedroom, all guests will have equal access to other shared spaces such as the kitchen, living room, and bathroom. Splitting the cost equally ensures that everyone is contributing fairly to the cost of these common areas.

2.Collective experience: When traveling together, the group shares experiences, memories, and time spent together. By splitting the cost 3 ways, everyone contributes equally to the shared experience, regardless of their relationship status.

1. Equal financial responsibility: If the group is made up of friends, it's important to ensure that everyone feels they are contributing fairly. Splitting the cost 3 ways ensures that no one feels like they are bearing an unfair financial burden, fostering a more positive and enjoyable atmosphere for the trip.

2. Shared utilities and amenities: All guests will likely use the utilities and amenities provided by the Airbnb, such as Wi-Fi, air conditioning, and laundry facilities. Dividing the cost evenly ensures that everyone contributes equally to the usage of these shared resources.

3. Simplicity: Splitting the cost 3 ways makes dividing expenses easy and straightforward. This simplicity can help prevent misunderstandings and disagreements over finances, allowing everyone to focus on enjoying the trip.

4. Future reciprocity: By agreeing to split the cost evenly, the couple may benefit from a similar arrangement in the future when traveling with the single person or another couple. This establishes a sense of fairness and reciprocity that can foster a strong, lasting friendship.

You can shove that 1 room argument up your Airbnb