Spirit has round-trip flights from Dallas (DFW) to Panama City (PTY) for $276-$286 with a connection. Flights April to May. Mostly midweek. Origin/Destination reversible.
Note: Spirit fares do not include a free carry-on bag. Only a small personal item, like a Jansport City Scout backpack is free. You can avoid paying for seat selection if you accept the randomly assigned seat prior to boarding.