at least with airlines, extras are optional.
Although I did find a travel agent, who charged less, the more passengers in the booking.
We had another family looking at doing same as us.
Airfare to USA in peak season was $1500 each for 4 of us, but if other family of 5 booked same flights, at same time in same booking & we made no more than 2 payments at same time, the price dropped to $1440 each(all adults). Guess there was not twice the work involved.
So it can pay to find a travelling companion, even if you don't share the same room.