The Freedom E-bikes kit is a 250 Watt system using a 36V motor. This is the max allowed in the EU & UK anyway.
Its not just because of the battery that it is the lightest. The motor only weighs 2kg and the controller 100gms. In most other ebikes the hub motor alone weighs more than the whole Freedom Ebike kit!

Its also not a premium price. At £470 pounds (US$790) for the basic kit (incl hub motor in wheel, battery, throttle & controller) its substantially cheaper than most of the competition. Even if you add another 2 battery packs (£200 for two extra packs) to bring the capacity to 273 W/hr, its still slightly cheaper than the competition.
But frankly, e-bikes are about functional transport, not long distance recreational riding and who really commutes more than 30km (2 battery packs) on an ebike?

Batteries are a big part of the cost of an ebike kit and the Freedom E-bike kit gives the consumer the choice of how much battery capacity they need and want to pay for.