Not getting into fuel or insurance or campgrounds or depreciation, maintenance including tires for us has been just short of 1100 per year for the last 10 years. We are full timers so in it most of the time except when we are in our little C or tent trailer. First set of tires lasted us 9 years, had to replace the fridge and had some other minor stuff, lift pump, water heater board 3 TV's etc. We don't change our own oil or filters but do the rest of the maintenance and repairs ourselves. Probably 7000 miles per year avg, I think I have a few fixes coming up and a carpet to replace with laminate. One of the furnace motors is getting squeaky, need to replace both slide toppers. Fuel hasn't changed much in the last 4 years so hard to predict what will happen there. I think it will be steady for another 3 or 4. We are about 10 years into our 20 year full timing plan. Still totally affordable, still love our coach.
Good luck.