Honda CBR125. A 2000$ city bike that does ~100-120mpg wrong gallon >70.
As long as it costs more than $1 to go 200 miles, it's going to be more expensive in the long run. 70mpg is approximately $15 for 200 miles. Theoretically, anyway, since this requires the assumption that the vehicle will last forever, which it probably won't.
Anyway, I'm more looking for a personal vehicle for getting myself around that won't be classified as a motorcycle, since that would require a second license. I'm hoping this one won't be, simply because you don't seem to ride it like one at all.