Low fare carriers don't operate this short route, so there is no competition. Also, it's likely that it's a connection route and most people are likely to drive MCO-MIA than take a flight.
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When once you have experienced being a 1K, you will forever fly the friendly skies with your eyes set on 100% mileage bonus and SWUs, for there you have been, and there you will always long to return, every year!