I think it should be noted the fares quoted above do not include segment fees and passenger facility charges. Because these fees are both segment based, not fare based, they can range from $8.50 to $29 per roundtrip, which will be added to the base fare posted above.
In addition to the number of segments which comprise your itinerary, different airports assess different passenger facility charges, ranging from $0 to $4.50 per segment.