Southwest has round-trip flights from Chicago (MDW) to Dallas (DAL) for $98-$103, NONSTOP. $49-$53 each-way. Flights vary depending on destination, mostly between February and May. Mostly weekday/midweek flights. No Holidays. Origin/Destination reversible.
Note: You can save up to an additional $150 if you purchase your Flight+Hotel together as a package on Southwest Vacations and use the US150OFF coupon code.