The Jungfraubahn's fare policy is somewhat "byzantine" to say the least... and has been the subject of much debate on these Forums. This morning (after much trying yseterday!) I managed to get a real live person in their office on the phone and asked her several questions to which I think I got correct answers...
1. Swiss Pass, Swiss FLEXI Pass being used that day as a Swiss Pass and Swiss Flexi Pass being used that day as a Half Fare Card:-
25% discount from Kleine Scheidegg to the Jungfraujoch Cost per person, round trip, is 90frs.
2. Half Fare Card (whether One Month Tourist HFC OR normal Swiss HFC):-
50% discount. Total fare from Lauterbrunnen to the Jungfraujoch 88.10frs
3. Day ticket (Tageskarte or Carte Journalière) bought in conjunction with a normal HFC:-
50% discount from Wengen to the Jungfraujoch and back to Wengen
I am not at all clear why some discounts begin at Kleine Scheidegg and others at Wengen. But that is what I was told, so I have to accept it. So to sum up:
Normal (one month, year etc) HFC Lauterbrunnen to Jungfraujoch 88.10frs
Day ticket (71frs*not included) with HFC Lauterbrunnen to Jungfr. 88.10frs
Swiss Pass, Flexi Pass Wengen to Jungfraujoch 94.50frs
or Flexi as HFC Laut. to Jungfraujoch 129.60frs
*Day tickets for use from early morning, 2nd class = 71frs
Day tickets for use from 0900 onwards 2nd class = 58frs
Day tickets early morning 1st class = 121frs
Day tickets from 0900 on 1st class = 96frs
You can also buy "multipacks" of Day Tickets which reduces the cost a little.
Hope this is some help in finding one's way through the jungle! And one more thing... on the Jungfraubahn Lauterbrunnen to the Jungfraujoch there is no 1st class!!