I had my last motorhome for 5 years and this is my actual cost of ownership. You can throw out any part that you don't want to count but this is what I believe it cost me. It was a 2003 model that I bought in 2011 I sold it for $20k less than what I gave for it, which I thought was not bad. I did most of the repairs myself. This is the actual cost.
$20k at 5 percent interest = $377 per month
one set tires = $2400 or $40 month
6 batteries = $840 or $14 month
Inside storage = $80 month
Annual oil change & upkeep $1200 or =$100 month
this includes an engine water pump, a fuel pump, shocks, various other PM repairs including water heater failure and fridge repair. Fridge was weak and needed replacement.
Insurance, tags and taxes = $100 month
Total cost of my ownership = $711 a month or $8,532 year or $42,660 for 5 years of ownership.