Yea I think you are right. I've never considered motorcycles particularly cost saving vehicles especially compared to a car. Even in the gas shortage years in the 70s when I was selling bikes and people came in wanting to save money by driving a motorcycle to work, instead of a car, I thought " if you only knew". Sure the gas mileage is better, but frequent tire replacements, oil changes, brake pad replacement, oil/air filter replacements, spark plug replacements, valve adjustments, chains and sprockets etc just drive the cost of owning a motorcycle through the roof, especially if like me you don't do your own service work. (I do change my own oil, but thats about it).
I get a discount at my local shop but a set of Michelin Road 5s installed still cost me $560 ($470 for tires and $90 for labor). Since I got 8,304 miles out of that last set of tires, that works out to just over 6 1/2 cents per mile.
Good thing motorcycles are fun is all I have to say.