While DFW-LGA has been long discussed given AA's monopoly and you're right, they can charge whatever they think they can get, I have noticed a definite increase in AA's prices.
For the last three years, I've gone NYC-MIA once a month on weekends and could usually get $225ish fares with a little bit of planning. Now, nothing below $275 and more frequently $350-$450. I'm sure a result of reduced capacity and the like, and good for AA if they can keep their planes full at those prices, but certainly a change.