Motorcycle gives you speed, but if you have to cross a river and there is no bridge intact, it's a bit much to carry. A dirtbike might make more sense, and they are cheaper.

I would say the bulk of the fuel for the motorcycle is less than that of the bicycle's motor, so that evens out the higher parts count.

Just thoughts from the guy who's B plan is a good pair of boots and some spare socks. :P