There comes a point when being cheap about splitting the cost ruins everything. I haven't shared with a couple myself and wouldn't want to, but 50/50 seems reasonable as long as it is equal beds, such as double/double.

One time I took my two elementary school age kids to the World's Fair with a friend of mine. We had two rooms. I expected to keep both my kids in my room. Then when we got to the rooms, she saw she had two beds and invited my little girl to stay with her, which made my child feel very special. And then when we got home, she wanted me to pay for half of her room.

I paid it to avoid bad feeling but it felt wrong to me. What do you think?