Unless you're ordering a flight of craft beer, flights don't get much cheaper than this. Right now, Norwegian Air Shuttle has dirt cheap flights available on their Low Fare Calendar, including a round-trip from New York City to Copenhagen for just $286 throughout January and February 2017 (more cities below). Flights are popping up for as low as $306, but thanks to a nice little conversion tip from The Flight Deal, those tickets can be had for $286.
To get yourself to Copenhagen, head to Norwegian's Low Fare Calendar and move to the Norwegian Denmark website. You'll want to book your flight in Danish Krone. The current conversion rate will save you those few extra dollars, which you can spend on whatever the hell you want, in Denmark.