The cost of an RV depends on whether the RV you buy is a travel trailer, fifth wheel travel trailer or a motorhome.
The cost of an RV also will vary depending on the size of the RV.
For a smaller Travel Trailer they can cost from $10,000.00 to $18,000.00 for a brand new travel trailer while some motorhomes can cost from $25,000.00 to $60,000.00 and even as high as $200,000.00 or more for really luxury based models of motorhomes.
RV's and travel trailers as well as motorhomes do depreciate pretty quickly as well so when you drive off the lot with an RV or travel trailer you'll be losing money quickly.
If you plan to just use an RV for camping once or twice per year then it's usually best to just rent the RV instead of buying it but if you want to camp more often or hate renting the RV and have the money to buy then buying an new RV can be worth it.
Just remember that you'll never get all your money back if you do decide to sell the RV when you no longer want to use it or need it.