You didn't say where in Hawaii your son wants to go, but Alaska Airlines (AS) is currently selling one-way tickets from San Francisco to Honolulu on 1/28/11 for $280 plus tax ($301.50 total). All of AS tickets are priced as one-way tickets. They will get more expensive if he waits until the day of the flight. Full-fare coach on the same flight is $501 plus tax ($522.50 total.)