Lot's of very good information and valid points in this thread. I make two annual treks between California and Alaska and have done it both ways, towing a 17-foot
Bigfoot and either
boondocking, or staying in RV parks/campground, and a few trips with no trailer and staying in hotels every night. I lose about 40% of my fuel economy with the trailer.
I've noticed that in the U.S., the cost between each scenario is pretty close. But in Canada, where petrol is expensive even on a good day, the difference in cost is greater, with a slight advantage going to the hotel route even though hotels are also expensive in Canada.
However, when I factor in the dogs, that is a bit of an equalizer since most hotels now charge a non-refundable per pet fee (as opposed to a refundable deposit like they used to do). Those fees can significantly jack up the cost of the room since I have two dogs. Most campgrounds and RV parks on the routes I travel don't charge a pet fee. That seems to be more of a thing in parks in or near urban areas.
So, at the end of the day, if I travel with my dogs, it's pretty much a wash. But if I factor in the average fixed costs of owning the trailer (purchase price, storage, maintenance, supplies, etc.) it costs quite a bit more than the hotel route when everything is averaged out.
If I travel in the winter, which I have done a couple of times, the hotel route is definitely cheaper since you can usually only camp on the warmer portions of the route and as you get farther north, you end up hotelling it anyway. So even though you are still paying the mileage penalty with the trailer you end up also paying for rooms for a portion of the trip. It's a double-whammy
I still prefer the convenience and other benefits - most of which have been mentioned in previous posts in this thread - of having the trailer with me but on a cost basis alone, the hotel route is much more economical in my case.