Berlin from $410 roundtrip

Boston to Berlin early summer deal
$410 Round-Trip
Norweigan Airlines

Los Angles to Berlin late spring deal
$420 Round-Trip
WOW Airlines

Miami to Berlin MID SUMMER DEAL
$440 Round-Trip
                                                                                    WOW Airlines

Dates for travel to Berlin can be played around with on Google Flights.  Also you may want to try finding good dates on Google Flights, then moving over to the airlines website to see if they have promotions running to save even more.  WOW airlines has been running 2 different sales this spring.