This really depends on the motorcycle / scooter. For example, my KLR650 is less expensive to operate than my Aprilia 250. The Aprilia gets better MPG, 75 vs 50-55, but I spend far less on tires on the KLR. Compare my KLR to a big Maxi scooter and the KLR will come out ahead easily. A big part of the cost of any scooter or motorcycle is maintenance. If you do your own maintenance is saves a bundle. For example. I change my own tires on my dual sport bikes, but not street bikes/scooters with tubeless tires. I adjust my own valves but not sure I would want to tackle some of the more complex bikes out there. And what about valve adjustment intervals? Typically they are longer on motorcycles. Of course, if you're commuting on a GSXR 1000 or just about any other large motorcycle, then the most scooters will be cheaper. It would be interesting to compare a V Strom 650 to a Burgman 650. I'd expect the V Strom to be cheaper to operate. However, I don't ride purely based on what is the cheapest. I ride because it's fun. Saving money is important to me, but not the most important thing.