Depends wildly on how much you use the RV. I suspect many use it 5-6 weekends and a 1 week vacation per year...yep, it's wildly expensive way to travel.
But for those who plan to utilize it a lot, the costs come down very quick.
The other thing is to look at the type of RV you buy and how much maintenance you can do yourself. A big DP MH where you outsource everything to repair shops, it's going to be very expensive. A small bumper pull travel trailer pulled by the 1/2ton pickup you already have for other reasons and you do most basic maintenance yourself...it can be pretty cheap.