United Airlines has Los Angeles LAX to Miami MIA at $106.60 each way for departures in September and lots of availability from $123 to $127 each way into December.
Both American and United Airlines have SFO or LAX to Miami at $233.20 round trip for September to December departures. American has some nonstop flights available for $30 more. These are primarily Tuesday, Wednesday and Saturday flights.
United Airlines Los Angeles LAX – Miami MIA
$213.20 Tuesday September 22 – Saturday September 26
Flight Miles: 4,686 miles LAX-IAH-MIA-IAH-LAX (via Houston) in economy N class.
American Airlines San Francisco SFO – Miami MIA
$233.20 Tuesday September 29 – Tuesday October 6
Flight Miles: 6,086 miles SFO-ORD-MIA-ORD-SFO in economy O class.