Let's say you have 5 people (one over the room limit), are you really going to get another room that cost a few hundred per night (times two, since you have two rooms) with an extra bed.
I am not sure how many of those are in a couple, but I wouldn't have 3 people in one bed none the less. Generally speaking I would get a 2-3 bedroom resort suite that has a pull-out sofa, everyone has a place to sleep. With 5 people sharing the cost it ends up not that much.
Nah, beaches aren't cheap to go to. The most popular beach in Texas (South Padre Island) has some rooms for over $400-500 per night. These are the "Resorts".