A number of the major carries offer year-round flights to Costa Rica. Most flights go into San Jose, but more and more flights are being offered into Liberia. Departure cites can have a major bearing on price; more so than you'd expect in some cases. We once priced a first class flight from Las Vegas to San Jose and then priced another first class from Los Angeles to San Jose. The L.A. trip was $800 less and a flight from Vegas to L.A. was only $150, so it was well worth it to shop around.