It *can* be cheaper than staying in hotels but it's really two very different ways of traveling so it's tough to compare. For us, RV'ing allows us to take our 2 dogs, which saves us at least $75 per night in pet boarding fees. We also bring a paddle board, kayak, and fishing rods with us.
But here are some numbers for you: we used our RV around 2 months last year, traveling 9000 miles. That's quite a bit of usage since I still have a full time job. It cost us around $140 per night, which includes the cost of fuel, RV park/state park fees, insurance, and storage. This doesn't take into account the depreciation on the RV, which is substantial. If you factor in not having to pay for pet boarding, our per night cost is effectively much less. Again, perhaps not a great comparison to staying in a hotel but some data for you to consider.