Round trip vs. One way fares
 

How do the airlines get away with charging far less for a round trip ticket than they charge for a one way ticket of either of the legs on the same round trip ticket? A one way ticket should cost half of what a round trip costs, right? I don't understand how they even justify this internally. I assume they do it because they want to ensure (coerce) you don't switch to a different airline for your return. Does anyone know how they get away with this and if the congress or a regulatory agency has even considered prohibiting this outrage?

There is no regulation of fares in the US. The airlines assume that one-ways are predominantly purchased by business and it is market driven, the pricing is not based on cost, it is based on demand.

Some airlines fares, notably Southwest and Frontier, are all sold on a one-way basis. You're free to fly them one way, or roundtrip.

People make the assumption that fares are calculated based on the number of legs or the distance. That is not the case. Fares, whether one way or round trip, are priced based on demand, as Jim pointed out.

You will find in certain circumstances that a one way ticket is less than a round trip ticket. In many markets, however, one way tickets are purchased more often and are in higher demand - especially among business travelers, which make up a large majority of airline travelers. The airlines will price those higher due to that demand. They are a business operating to make money, like any other business, and have the right to do this, just like any other company has the right to charge more for products or services that are in higher demand. I doubt congress will do any thing about that, or even can.

AA alot of times has 1 way fare sales. i've purchased 2 one way tickets (ord-FLL) and FLL-ord for $59 each way last year as a roundtrip ticket was around $220