The poster asks why rent a camper to camp at Fort Wilderness. My guess is that it would be a great way to try camping in a friendly and easy spot.
As others have said, if you have to pay to rent and for the site, you probably won't come out ahead. But, consider your food tastes and expenses when doing the math. We eat at a sit-down restaurant each day and get snacks in the parks. However, with the camper, we can make breakfast and usually one other meal each day. That allows us to eat the food that we like and to keep the costs down a bit.
The real reason to camp at the Fort is that camping provides a very different experience than staying in one of the other resorts. I have stayed at several resorts; Polynesian, Contemporary, Wilderness Lodge, and the Dolphin. They are all really nice. But, at the Fort, we have some outdoor space. On our last visit, the kids set up a badmitten net in the sand area. We had a great time playing as a family - something that would not have happened at the other resorts. We also did a bike ride to the Wilderness Lodge on a nice trail. Again, we probably wouldn't have our bikes along if we were at another resort.
We originally bought our camper for a trip out West to see the National Parks. But, we have really enjoyed the family time it enables. We camp at many different kinds of campgrounds, from State Parks to RV Resorts. We have stayed at the Fort twice. And, we have an upcoming reservation to do it again (and hopefully a few more times after that). It is really a great experience and I highly recommend it.
the eman