My guess is because that flight goes from one ex-AA hub to a current AA hub (although you didn't know that just by looking at it).
But even if what you said is correct, you admit (indirectly) that you realize that simply raising the fare is not the answer. It's a balancing act in trying to maximize revenue. If AA sold three tickets on their plane in the above scenario for $50,000 each they'd certainly make a bundle of money - the trick is unless they have some amazing marketing and salesmen, that ain't gonna do that

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