It’s basically a car, so yes you’re “upside down” but cars aren’t investments so who cares. You’re not supposed to get what you paid for it, you’re supposed to use it.
The money angle was the original question (How Do People Afford This). So depreciation, repair, fuel, etc, all figure in.
For folks who travel a couple of weeks a year, an RV would be economic idiocy, unless they really love the lifestyle and have money to burn. If you "live" on the road most of the year, yes, it can make economic sense. Lots of folks live that way, and really enjoy it.
Yes, cars aren't investments, but you pretty much have to have one to function in everyday life. RV's are not necessary to travel, so it's a choice. But you better put a pencil to it.