Biggest expense of owning most RVs, TT or otherwise, is often the cost of the money it took to buy it: interest on loans, lost income on savings, and depreciation of value. You can reduce those costs by buying cheaply, used and fairly old, so there is not so much money tied up and depreciating.
Second biggest expense for me, owning, has been cost of insurance and storage. Like the cost of money, these are expenses paid whether using it or not.
The biggest expense of using it (as opposed to owning it) has been the fuel cost of moving it around. It costs about 50% to 100% more per mile, towing most medium size TTs, compared to driving the tow vehicle without towing. Could be a whole lot more than an economy car.
Thinking of it as alternative to hotels, you need to work the numbers. When traveling to get somewhere, I like to cover 450-500 miles a day. RV traveling tends to cut that to about 300-400, I like to set up camp in time to fix dinner, break camp after breakfast, it limits my driving hours.
Consider my trip to Michigan to visit family (900 miles each way, several times a year), or visiting my brother in Florida (1200 miles each way)
My RV: 900 miles @ 7.5 mpg, 120 gallons at $3.00, $360 for gas; two nights RV park at $40, $440 total.
Subcompact car: 900 miles @ 36 mpg, 25 gallons at $3.00, $75 for gas; one night Hampton Inn or HI Express, $100, $175 total.
My van: 900 miles at 15 mpg, 60 gallons at $3.00, $180 for gas; one night hotel, $100, $280 total.
My van pulling TT: 900 miles at 10 mpg, 90 gallons at $3.00, $270 for gas; two nights RV park at $40, $350 total.
But consider an extended vacation, no relatives to stay with for free and eat their food. Dallas to Yellowstone NP, and back, for a week at destination.
My RV: 3000 miles round trip, 400 gallons at $3.00, $1200 for gas. Four nights each way enroute at $40, $320. Seven nights at destination RV park $350, $1870 total.
My subcompact: 3000 miles, 83 1/3 gallons at $3, $250 for gas. Three nights each way enroute at $100, $600. Seven nights in the lodge at $300, $2100, for $2950 total.
Lodging costs are different at different destinations, different locations, different parts of the country. For example, to park your RV close to New York City might cost $80 (plus transit fare) but a midtown Manhattan hotel might cost $350-500. Difference is less at Walt Disney World, where Fort Wilderness can cost as much per night as an off-property hotel room.
But the principle applies. The more you move the RV, the more expensive it becomes relative to staying in hotels. The longer you stay in the RV without moving it, the more you save on lodging, to make up for the cost of using it.
But if you own the thing, there is also that cost of ownership, whether you use it or not. First couple years on mine, early in the depreciation, it was costing me more than $500 a month to own it, so I was inclined to use it constantly. At almost 10 years old, cost of ownership is about $120 a month, I am more inclined to let it sit, drive my car to visit family, or fly off to Europe for 2-3 weeks at a time rather than make a RV road trip.
The way I mostly use the RV now is I haul it to a campground on a lake, where I park it for $8 a night, and the location is 15 miles from my house, so a $15 round trip. There is no hotel option, but I could throw my tent in the back of the car, still paying $8 a night for the campsite.
I don't RV to save money on travel, because most of the time it doesn't work that way. I RV for the outdoor lifestyle, but even then, you might find that a cabin in a state park or in a RV campground is close enough in price to a campsite that you might save enough to pay for the extra gas if the stay is less than a week or two and the drive is a couple hundred miles.
One last thing. We bought a TT in 1961 to save money on a single trip. We needed to take 10 people out to a relative's homestead in rural Montana, where the nearest lodging was a 140 mile round trip and we would have needed at least three rooms for two weeks. We dry camped on the property for free (ranch didn't have electricity or running water). What we saved on lodging at destination paid for the TT and the extra cost of hauling it 4000 miles. The big difference was gas was about 28 cents a gallon, and motel rooms were $15-25, campsites $2-3. A much bigger difference than today.
