What are the costs of 1 hour flight in modern low-cost airlines?
For the low-cost model there's an article called The true cost of flying revealed, which uses a 154-passenger A320 for its figures.


  According to the calculations, each passenger on board an Airbus A320, which has a capacity of 154, costs the airline $68.50 (£47.06) for the 260-mile journey.
  
  The one-hour flight costs the airline an estimated $2.50 per passenger [for fuel].


The total cost equals \$10,549 per hour "with profits as low as \$10 [per passenger] on some flights".

Also from the article—


  If you want to be a millionaire, start with a billion dollars and launch a new airline.— Sir Richard Branson