andrasz
You prioritized passengers over cargo ("so there is not much cargo space left with a full pax load, 3-5 tonnes at most."). If the order of priority is pax+bags and then fill the remaining available lift capability with cargo, it will loose money as you claim. If the order of priority is cargo, then fill the remaining lift capability with passengers and bags, routes more often become profitable, or at least break even. This is why Norwegian's lack of communication to its front line workers was so fatal. Crews and operations folks would refuse cargo to accommodate passengers and bags, when the route was opened on the basis of the cargo contract. This is why the route was closed when the shipping agent cancelled the contract.
It has been said more than enough times, and validated in financial reports, that there were aspects of Norwegian's long haul operation that worked, and worked well. LGW to the US, and OSL to the US was making money overall (and I believe, but am not positive, that OSL/CPH/ARN to BKK was strong as well). LGW to South America, and CPH/ARN/CDG/AMS/BCN/MAD/FCO to the US were money losers. Norwegian expanded too much and too quickly, and the debt incurred could not be sustained with trying to carry all the unprofitable routes. I strongly believe if Norwegian has expanded a bit more slowly, and only operated 10-14 787s with limited routes, it would have worked.