San Francisco to Costa Rica $542 RT FIRST CLASS on Delta Airlines (travel March-June)

Delta Airlines have round trip FIRST CLASS airfares travelling from San Francisco (SFO) to San Jose Costa Rica (SJO) for $542, making 1 stop.
Travel availability:
Departs SFO: March 7; April 11, 12, 20, 24-26, 30; May 2-5, 9-10,14, 16, 17, 23-25, 28-31; June 1, 4, 6
Returns: March 14; April 18, 19, 27; May 2-3, 7, 9-11, 14-16, 21, 23-24; June 1-2, 4-9, 11, 13
Use dates and book it on Delta Airlines directly. Two sample itineraries attached below showing one week travel and first class service.