That difference makes the article rather uninteresting. It's clear that the highest grossing flights are just the ones which are the most common and most costly

That difference makes the article rather uninteresting. It's clear that the highest grossing flights are just the ones which are the most common and most costly. In that kind of situation, airlines might even be competing as loss leaders: strategically operating at unprofitable levels in order to win market share and make up the difference on other flights travelers take. That is, there's a good chance in my mind that not only are these route not the most profitable, they could be the least profitable.