There is a P fare for this route. But LH P fares are notorious for longish minimum stay or strange rules. In this case:

TRAVEL FROM TURNAROUND MUST COMMENCE NO EARLIER THAN
THE FIRST SAT AFTER ARRIVAL AT THE TURNAROUND.
OR - TRAVEL FROM TURNAROUND MUST COMMENCE NO EARLIER
THAN THE FIRST SUN AFTER ARRIVAL AT THE
TURNAROUND.

P round trip is listed at 484€.

It is helpful to uncheck validate fares in order to see every fare and check out the fare rules If you are doing any kind of price research.

The step price increase sucks. But keep in mind that there is a handful,of different fares that map to a booking class. One day you get a dirty cheap D fare. On other days you pay crazy money for a K fare.

Cheers Alex