The Dahon Jack folding bike. It weighs 28.4 pounds (or 12.9 kg). I’ve treated this bike harshly for a year now, and I haven’t had any problems with it. It costs $459.
The Dahon Espresso. It has 21 gears instead of 8. It weighs 13.3 kg (or 29.3 lb). I’m currently testing this bike — so far it been as durable as the Dahon Jack. Update: My wife loves this bike, good maneuverability. It’s available for $370 from Amazon.