Here's the rub: We didn't buy a trailer to save money in the short run. (Perhaps the long, two-decades long, run.) We bought it so that we could explore places we'd be less likely to see if we restricted ourselves to hotel-based vacationing. Last month, for example, we went on a 9-day-long trip, stopping at four different campgrounds (only one of which did not have a shower) without ever having to pack and unpack. While walking around one of the places we camped (Salt Creek Park, near Point Angeles on the Olympic Peninsula) we saw one or two gray whales. Across the Straight of Juan de Fuca in British Columbia at Weir Beach Resort I saw a pod of orca (killer whales) while I was walking back from the shower. We likely would have missed these things if we restricted ourselves to a hotel/motel vacation.
We also got a trailer so we could be more spontaneous. Having fun somewhere? Trailering makes it easy to extend your stay. See something you'd like to explore? Pull over and look! Bored? Weather bad? Move on! When you're trailering the whole continent is your play space, so wander until you see something that catches your fancy.
Now, since your wife is doing the dollars and cents, here's something else to consider: Food. Stay in a hotel and you'll almost have to eat out. Stay in a trailer and you can cook a meal "at home" or microwave
something from Budget Gourmet for a fraction of the cost. (And my cooking is a lot healthier than much of the stuff we'd likely get from the combination of restaurants and fast-food places we would ordinarily stop at if we didn't have a kitchen.)
Lynne and I spent slightly over $100 a day on our last vacation (not including two ferry trips, which cost about $105 each). That's less than most hotel room after taxes, yet it includes everything we spent money on: gas, food, a few meals out, trailer park fees, odds-n-ends, a kilo (2.2lbs) of Smarties (my favorite candy), a few knick-knacks and one inexpensive (but nice) piece of artwork. So, if we're not counting the cost of the trailer, we likely spent less than half of what we would have spent if we stayed at hotels and ate out. Probably much less than half, actually.
Now, thinking of the up-front costs, there is a sizable expense involved in buying and possibly upgrading/refurbishing a trailer, but don't forget you can get a lot of that back if you decide trailering isn't for you and you decide to sell it.
The option to sell your trailer if things don't work out substantially reduces the amount of money you're placing "at risk."
Just some things to think about.