last question first. euro vs dollar vs krona vs yen. where are the models manufactured, look at the exchange rates. some develop ecu's in house, while some use "generic" controllers. some manufacturers are indeed more expensive than others, it costs different companies different amounts to produce the unit, and then in turn determine what profit they want to see. some are sitting on "older" designs while others continue to roll out new products or improvements to their design.

the difference between the 19 lb motor and the 36 lb motor are first not identical engines. there are different diffusers, different combustion chambers, other internal components, and more time is spent on the balance of the higher thrust motor to accomodate the higher rpm. essentially the rule of thumb would be the higher the thrust, the tighter the tolerances.

the 12lb class is the anomoly. you are right in that they should cost the same. my only guess is that the market would not cooperate.