I did an assumed budget for what I considered the fixed ownership costs before I decided to buy, and have kept a tabulation over the past 5+ years since I bought. This includes maintenance, repairs, depreciation, insurance, but not variable costs like fuel and other dollars that get spent depending on use.
This is a bit weighted favorably since it is based on a smaller Class C, but the only real difference might be depreciation. It was also based on buying new, and owning for 10-12 years, spending comparatively more up front but getting the benefit out of probably avoiding any major chassis or house repairs/replacements. I also do just about all my own work too.
Insurance annually: $750
Maintenance per year: $1,000 (2x a year oil changes, tires every 5 years, trans and diff fluid every 5 years, plus random misc. stuff to fix)
Depreciation over 10 years ($40,000, difference between $55k purchase price and hypothetical $15k end value): $4,000 a year average
So, $5,750 a year, the bulk of it depreciation. Actual out of pocket, $1,750. We do very little pure camping in it, using the RV instead as a home away from home at race tracks all over the country as part of my club stuff and my son's lower level pro events. We'd be in hotels 40-50 nights a year if we didn't own it, and that tab would be more than the total ownership cost. My friends bust me on my "racer math", but the expense is worth it.