American Airlines has round-trip flights from Dallas (DFW) to San Jose, Costa Rica (SJO) for $360, NONSTOP. Flights April, May, and August. Weekends available. Origin/Destination reversible.
This is a better deal than the United fare that was recently posted due to the free carry-on bag, and NONSTOP routing.
A Carry-on bag and also a personal item is allowed for free on American. You can avoid paying for seat selection by accepting the randomly assigned seat at the gate.