I don‘t know where you‘re eating lol. A döner in zurich is about 14-15 francs at the moment never seen one for 18 francs and they increased prices the last two years as well.
If you‘re having a meal and drinks for 50 francs per person you have likely been to a fancy restaurant. Don‘t get me wrong, it absolutely is possible to easily go over 50 francs, however its also is very easy to stay below that and still have a good experience.