United and Lufthansa has round-trip flights from Houston (IAH) to Amsterdam (AMS) for $493, NONSTOP. Flights from January to March. 7-day minimum stay required. Christmas / New Year blackout. Expect prices to fluctuate by +/- $15.
Note: Carry-on bag is allowed for free, but checked bags will have a fee. Upgrades into “Regular Economy”, which include a “free” checked bag are available for $531.
Note: This is a very good price for NONSTOP flights which normally cost about $1100.