Great points all around. I still hand calculate MPG after almost every trip, and keep some of the stats in a tab on my spreadsheet where I track towed miles and nights camped.
The MPG and fuel costs tracking are mostly to keep an eye out for changes that would indicate and unscheduled visit for a check-up.
Although our food costs are almost identical to if we stayed home, I observe the other things that are not economical about RV camping (e.g. how many more paper towels we use because we wipe our plates down to minimize gunk in our gray tank).
But separate from purchase costs, I'm pretty sure our operating expenses are less than if we took 1 or 2 traditional vacations a year. Way worth it to get away virtually every other weekend for 8 months a year.