Yep - biggest variable is type of bike/tires. A sportbike? Not so much.

If I were commuting, I'd look hard at a DL650 V-Strom. Ugly as sin, but: 50mpg, relatively cheap tires which can go 10~15k, low-maintenance bomb-proof motor/driveline, and it's capable of hauling ass both off-road & on (had a real eye-opening L-Day weekend riding with a guy & his wife on one :?: ). Damn skippy a ride like that could be a money-saver over an average-mileage car/truck, and be much more than just a 'commuter'.