American Airlines has round-trip flights from Dallas (DFW) to Santiago (SCL) for $586-$594, NONSTOP. Flights in October. Departures on Monday, Tuesday, Wednesday, Thursday, and Saturday. Very few extended weekends available. Origin/Destination reversible.
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.