I paid $10K cash for the 26' trailer in my signature. I didn't insure it since insurance wasn't required and liability was covered by my car insurance. I have my own storage so I didn't need to pay for storage. Loan interest = $0!
If I kept to 55mgh I could get around 12mpg with my diesel. (RV drivers don't drive slow because they are Nervous Nellies... they drive slow because they are cheap! MPG plummets quickly as speed increases!)
For weekend trips to a close lake it was great! We had all our gear there and were right on the lake with friends gathered around the camp fire!
For a 700 mile (one way) 8 day trip to Yellowstone the trailer was great and we probably broke even on fuel costs vs a hotel.
For a 200 mile (one way) 2 day trip to the beach... we go for a hotel to save money.
After 9 months I sold my trailer for $10K. I definitely got my moneys worth.
My GF decided she wanted a Class C instead of the trailer so her and the kids could move around the cabin so she bought a 91 vintage Class C. It gets 5-8mpg and the distance to destination vs number of days stayed has changed significantly. I would never drive the Class C to Yellowstone because of fuel costs and it isn't nearly as comfortable as my Duramax pickup. My back wouldn't survive the trip to Yellowstone... and I don't have back issues!
She paid cash for the RV, no storage costs but has to pay for insurance. Fuel cost have doubled greatly limiting how far we will take it. Repair costs have also greatly increased.
My point being costs will vary widely based on your circumstances!