samoa air from my understanding is a small domestic service flying samoa to fiji. as they are a small plane i can understand them asking for, and needing, passenger's weights to determine fuel requirements for the trip. i know small sightseeing planes often weigh or ask passengers to disclose their weight for fuel calculation purposes. having said that, i think it is incredibly poor form to charge a per kg price for the following reasons :
- the seats are 1 size fits all so someone who is larger (muscular, overweight, pregnant, whatever) is paying more for the EXACT same amount of space
- the amount of fuel required & the cost of the extra fuel is not proportional to the increase in price
- this tactic only serves to shame and marginalise people who fall within higher kilogram amounts for whatever reason
- as this airline runs a small domestic service they are not able to install seating commensurate with their patron's needs (ie larger, more legroom, premium economy etc) and therefore this is simply a way to extort more money from those who weigh more than others.
personally, while i think airlines today get away with a variation of torture (economy on a 14 hr flight does resemble sardines in a tin

) at least the arrangement is fair.
economy seats at 1 price. premium economy (with additional services, seat width and pitch etc) at a higher price. seat width and pitch advertised for each class up front. everyone knows what they are getting into.
i fit in an economy seat even though it is a bit smooshy. but when we flew southwest in 2011, i prebought 2 seats for myself, just in case.
i didnt encroach on anyone, in fact i didnt even encroach on the empty seat, but after all the horror stories and so on, i figured why not? and you know, it actually made my journey a heck of a lot less stressful.
there were no judgemental glares from skinny people. there was no stress about being singled out in line or being forced to pay a full fare day-of-flight fee for the 2nd seat, i was treated politely and with dignity and was able to preboard even earlier than the rest of the early boarding party.
did i require 2 seats? no. i still fit in 1. but it was actually a great experience. i was entitled to 2 x seats worth of baggage allowance (didnt get to use it though as it was a domestic flight and my international leg had less awesome baggage policies) but if i was solely travelling in the usa then it would have been great. having a policy like that meant everyone was happy. i chose to pay a higher fare to obtain a little more space to be on the safe side, was treated well and got all the perks of that extra space and... knew exactly what i was getting into.
that kind of policy i support a heck of a lot more than paying per kg and getting absolutely nothing but public humiliation in return.