o.o who'd need a 100cc engine on a city motorcycle, unless you're street racing >,>
on mountains though i can see the reason of needing a more powerful engine, since going up a mountain does need more oomph.
also in terms of cost per mileage, it is indeed lower in electric vehicles, but not entirely lower.
note: i'm gonna base this calculations on the tesla roadster since thats a known practical electric car.
the tesla roadster has a range of 245mile per full charge, and it's battery capacity is around 67.2KWatt which is about 3.65miles per KWatt.
electricity cost approx per KWatt is about 0.32USD in my area, which roughly computes to 21.504USD per full charge or 0.088USD per mile!
edit: also, comparing the regular price of a car(25K-USD) to the tesla roadster(100K-USD) you'd need around 1,200,000 miles of mileage to recover the 75K-USD investments(you save like 8.4USD per full charge which is 245miles) although i should be comparing this to a similarly priced sports car.
edit2: tesla model S priced at 49K-USD has a mileage of 160miles at 40KWatt battery capacity, thats roughly 4miles per KWatt, needs about 365,000 miles of mileage to recover the 25K-USD investment.