Originally Posted by
seawolf
Not quite sure if we are talking about same thing or different thing. The quoted section would mean if changes are made after departure, the flown outbound get repriced as well using the historical fares in effect. So if OP dropped the return, the flown outbound get repriced as if it was initially booked as a one way rendering the remaining (return) flight coupons having effectively zero value if the lowest historical one way is a Y fare.
For LAX-LHR , as per the OP's routing - if the person held a O class r/t ticket and then changed to one way, the fare used to compare with would be the historical one way O fare - of which there is a fare od $151 - both plus taxes and charges
Subject to that being the valid O fare ( e.g. weekend vs midweek etc )
There isapproximately an additional $200 taxes for the r/t ticket plus and additional $200 carrier surcharge
$151 + $200 + $200 = $551 vs $386
This gives a residual value when changing the r/t ticket to o/w of $551 - $386 = $165
My point on why it is v unlikely to have been 2 x one way fares is that AA has no discounted one way fares from London to Los Angeles