Frontier has round-trip flights from Austin or San Antonio (AUS/SAT) to Jacksonville or Albuquerque (JAX/ABQ) for $28, NONSTOP. $15 each-way. Flights in August and September. Origin/Destination reversible.
Note: Be sure to check both SAT and AUS for availability, some dates only are available out of one airport or the other.
Note: Frontier fares do not include a free carry-on bag. Only a small personal item, like a Jansport City Scout backpack is free. Checked bags cost +$35 each-way. You can avoid paying for seat selection if you accept the randomly assigned seat prior to boarding.