I think you could prove either side to be more economical, two of the reason we like our summer vacations with the 5ver is because it's like having our house with us, bed, food, tv, bathroom etc. We will visit 5 places across the continent on our 3 week trip and we have everything we need. We also like the freedom of it, but don't we all. I went to the beach every summer most of my life for 2 weeks, it was great, but sitting on the beach looks the same day in and day out. We decided a few years ago to show our daughter the country and we couldn't be happier. When we first started I was keeping track of the costs etc to compare, with a used camper and 1 trip to Disney we were definitely ahead, bought a new used camper and I can't say the same thing and I don't care, we accepted this is the cost we will pay to see this country. I don't think I could ever go back to spending that kind of money on a beach house for a week AND have to share it with other people.
Sorry I got a little long winded to prove my simple point. Regardless, have a great time at OBX and say hi to half the state of PA for us.