Star Alliance member airline Asiana Airlines offers San Francisco to Hong Kong HKG $530.50 round trip today. Google Flights shows $531 round trip fare for dates from August 31 into November. The fare rises to $570 round trip for January to April 2016.
This is the lowest fare I have seen this year in my searches. United Airlines had $557 last April and $560 to $580 has been available frequently for Hong Kong from California. The low fare competition is probably due to nonstop flights between SFO or LAX to HKG Hong Kong. Most of the discount fares are for one stop flights, sometimes with long or overnight connections.
Asiana LAX-HKG fare was $570 when I wrote about this deal on July 31.
Asiana Airlines San Francisco SFO – ICN Incheon, South Korea – HKG Hong Kong
$530.50 Tuesday September 8 – Tuesday September 15
This itinerary has 5:30am inbound arrival from Hong Kong to Seoul and 4:30pm departure from ICN. Enough time on the 11-hour layover for a day tour of the city and you still arrive back at SFO at 11:15am on the date you left Hong Kong. That is one long day. Grab a window seat and sleep on the plane over the Pacific.