Swiss rail pass vs half fare card vs single ticket cost??

The fares actually do not vary, unless you buy Super saver tickets which are restricted to a specific train.
In general and when in doubt, the Half Fare Card is often the cheapest option. It almost pays for itself with Jungfraujoch alone.

Thanks very much for your prompt reply. When I went to the SBB website the first time and selected the Lauterbrunnen- Jungfraujoch and return trip, it did not show the half fare card as an option - but I went back to double check, and now it shows the half fare card. Not sure what is going on, but I have noticed quite a few glitches in the SBB site that are sometimes there and sometimes not... like sometimes I can't get the date box to autofill correctly when I select a date on the pull down calendar. Then if I navigate off the website and come back into it from the beginning, then the date box will autofill correctly. Maybe this is a browser or German to English translation problem.

Also, I did see different fares for the other legs, but perhaps that was because of different routing. May not have been exactly the same trip, just had the same departure and arrival stations. Could that be the reason for seeing different fares?

When you check fares, did you realize that the SBB site assumes you have at least the half fare pass? So double the price you see for the fare without any passes. However, you did say you'd been there before, so you may know this. I think the convenience of the Swiss Travel Pass is worth it, as there's so much else you can access, such as lake boat rides, getting up to Mt Rigi, museums and castles ( Chateau Chillon,) etc. When I went to Switzerland in 2021 there was a 25% discount the STP; perhaps you'll be so lucky. Hope you have a great trip in this beautiful country. Safe travels!

Thank you, Pat, for your comment. I am aware of the great benefits of the Swiss Travel Pass, and have used it a couple of times. So far I don't think it's the right answer for this particular trip. We will be visiting family in Neuchatel and some sites that are only of significance to our family and therefore not the usual tourist stops. Also Neuchatel has a free coupon book that the local hotels give you when you check in. The coupon book gets you free admission to the local museums, buses, and even a boat ride if I understand it right. With a little luck on the weather, the only things we will have time to do in Lauterbrunnen is going up to Jungfraujoch and visiting Trummelbach Falls.

I did make sure the train fares I used in my original post were full fare, not with the half fare card already factored in. It looks like the JFJ half fare mentioned by a previous post will get me to the point where the half fare card will make sense. I do appreciate knowing about a potential discount on the Travel Pass and will keep my eye out for that. A deep discount on the Travel Pass may make it the more attractive offer. Again, thanks for your input.

And I will make a note of your inside info on Neuchatel in the event I ever have the pleasure of a visit.

If the STP is ever discounted again, some sharp eyes will definitely post the info here. Have a wonderful time. If I could, I'd go to Switzerland every year.

If your total Full fare tickets per person is over 240 CHF, then the Half Fare Cards make sense. You should really do your calculations in CHF, as that is what everything is priced in Switzerland. Since your full fare tickets will be 375 CHF, with a Half Fare Card you would pay 187.50 CHF plus 120 CHF equals 307.50 CHF. A 4-day Swiss Travel Pass is 281 CHF, but it will not get you to the Jungfraujoch, only as far as Wengen. The rest of the way (the expensive part of the trip) you only get a 25% discount.

So it looks like Half Fare Cards are the way to go.