Delta, American, and Southwest have round-trip flights from Dallas (DFW/DAL) to New York (JFK/LGA) for $158, NONSTOP. Flights August to April. Weekends available. Origin/Destination reversible.
For Southwest flights, use their fare calendar to pull up the fare [linked in post].
Additional Savings: Sam’s Club is selling $500 Southwest gift cards for $449 [linked]. You can save an additional $50 on Southwest flights if you travel often enough or with a big enough group to burn through the gift card credit.