AA's Price & Schedule also allows mix-and-match for each direction, but still requires, in the end, a RT purchase. Certainly possible that it allows actual purchase of the OW separately, and it really is half the RT price. Hasn't been the case in the admittedly few cases I've looked at, though.
It would be interesting to see some concrete examples.
Cheers.
I'm not sure what's so difficuly about looking at fares at aa.com and seeing the difference but here's a OW and a RT I'm doing . $139.40 and 278.80
AMERICAN AIRLINES 1230 SEA Seattle Sep 27, 2010 11:55 PM DFW Dallas/ Fort Worth Sep 28, 2010 05:30 AM Economy O 13C Food for purchase CREATE
AMERICAN AIRLINES 406 DFW Dallas/ Fort Worth Sep 28, 2010 06:10 AM RDU Raleigh/ Durham Sep 28, 2010 09:45 AM Economy O 13C Food for purchase CREATE
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Fare Summary help
Average Fare per Person - 118.00 USD
Passenger Type Used in Pricing Fare per Person Additional Taxes and Fees per Person Total Price
1 Adult 118.00 USD 21.40 USD 139.40 USD
Total Price 139.40 USD
AMERICAN AIRLINES
1352
RDU Raleigh/ Durham
Oct 07, 2010
06:15 AM
DFW Dallas/ Fort Worth
Oct 07, 2010
08:10 AM
Economy
O
15B
AMERICAN AIRLINES
529
DFW Dallas/ Fort Worth
Oct 07, 2010
09:10 AM
SEA Seattle
Oct 07, 2010
11:25 AM
Economy
O
14B
AMERICAN AIRLINES
506
SEA Seattle
Oct 12, 2010
12:10 PM
DFW Dallas/ Fort Worth
Oct 12, 2010
06:05 PM
Economy
O
10D
AMERICAN AIRLINES
1702
DFW Dallas/ Fort Worth
Oct 12, 2010
07:25 PM
RDU Raleigh/ Durham
Oct 12, 2010
11:00 PM
Economy
O
11B
Fare Summary ?
Average Fare per Person: Departure - 118.00 USD Return - 118.00 USD
Passenger Type Used in Pricing Adult
Departure Fare per Person 118.00 USD
Return Fare per Person 118.00 USD
PriorityAAccessSM and Same-Day Standby Complimentary
Total Fare per Person
236.00 USD
Additional Taxes and Fees per Person 42.80 USD
Total Price 278.80 USD