I give you the Optima Dingo recumbent bike; it is now fitted with 4.99 buck carrier side bags (they take 52 liters of goods mind you). And I've done 60 km trips with 16 kg of goods locked away in these bags.

It runs on water and does about 100 km per liter (235 mpg). The only real drawback of this model is that the air-co is shut off each time that you stop. Top speed is only modest however; it peaks out at 45 km/h (30 mph). It corners like a jet fighter however.