This looks impressive
Ahooga eBike ? Light+ | Ahooga Bike
not tried it, just found it by googling lightest electric bike
Looks like a Brompton clone, but the battery seems pretty small at 24V/4.4Ah(105.6Wh) and that cut may be part of the lightweight story. I compare to my Dahon at 9.9kg bare plus 5.2kg for the ebike conversion, which carries a comfortable but heavy 36V/14Ah(504Wh) battery (and is way cheaper). From doing some research I guess the 10kg for the bike are about construction min unless you go highly expensive exotic materials, the motor conversion adds 2kg and the rest is trading battery capacity for weight.