American Airlines has a low $216 round trip airfare between Los Angeles and New York LGA Airport, beginning in September and available most weeks through May 2016. Low fare is available primarily for DFW one-stop route and not nonstop flights.
American Airlines New York LGA – Dallas DFW – Los Angeles LAX
$215.20 Thursday September 3- Thursday September 10
This as about as good as it gets for cross country round trip flights between the largest cities in the USA.