I tend to disagree on most opinions.
Let's say a room is 120$ and couple decides to share it with a friend.

If 1/3 each, it ends up couple pays 80$ and friend pays 40$. Well, for just 20$ more each, it would make sense to have a "private" room.
If it's 1/2 we pay, friend still pay half price (60$) and couple pays half price too (60$)

In my POV is fair to consider couple as a unit as they would share per person costs anyway

All this said, I would choose a cheaper hotel and have a private room