Via Secret Flying Expedia is pricing airberlin itineraries from Copenhagen to Berlin (possibly others, though likely requiring origination in Denmark) as low as 43 cents.
Here’s one way from Copenhagen to Prague. Note that itinerary choices show up at ‘regular price’.
The Czech flight continues to price the same if you click through, however the price of the airberlin one-stop itinerary drops.
Here it is for US$3.00:
Here we see it then at 3 Danish Kroner:
3 Danish Kroner are worth 43 cents.
When I go to complete the purchase, however, I get an error so it’s possible this isn’t bookable.