There's been a lot of helpful advice in this forum regarding Swiss trains and other travel inside Switzerland. I took one bit of advice and set up a spreadsheet to compare the cost of various travel options. For what it's worth here's what I found. It's probably not perfect, route cost information and discounts can be hard to find, and it covers our specific itinerary.

Day 1 - Arrive ZRH Zurich
Day 2 - Zurich center Zurich
Day 3 - Go to Grindelwald Grindelwald
Day 4 - Jungfraujoch Grindelwald
Day 5 - Mannlicher / Wengen / hike Grindelwald
Day 6 - Mr First / hike Grindelwald
Day 7 - Open: Interlaken / Bern Grindelwald
Day 8 - Go to Montreux Montreux
Day 9 - Castle / Gruyeres Montreau
Day 10 - Vevey / Lausanne Montreux
Day 11 - On to other areas by car

Costs refer to two people traveling and include everything I could think of. I hope you find the results helpful.

1. Full cost of trains, gondolas, lifts, busses = US$ 1,000 (yes, exactly)
2. Cost with half fare pass - $ 950 of which $245 is 2 passes for 30 days
3. Cost with Swiss rail pass - $1,420 of which $880 is 2 passes for 8 days
4. Cost with Bern. Ober. pass - $1,120 of which $714 is 2 passes for 8 days
5. Cost by car plus special lifts and trains - $1,090 with no passes

Interesting result I think. We'll use the half fare card, it will also help us later. We won't travel enough to save money with the expensive rail passes, mainly because they give small discounts on the Junfraujoch train which costs $200. If you were going for longer the passes get more effective. If you included boat trips the passes would save you more.

The other thing is that these numbers are pretty close and personal preferences or convenience may be more important than the estimated savings. Good traveling.

Sorry about the formatting. The city at the end of the "Day x" line is the hotel city.

Thanks for reporting on your research. I think you'll be pleased to use the Swiss rail system!

Nothing new: the more you use a pass the cheaper it is.

Nice of you to share your results. When we went in 2016, we basically built the trip around using the 15 day travel pass and used it every day (save one), so that worked out well for us, but for most folks who spend a week or more in Switzerland, the half fare card usually wins the math contest.

Thanks for the feedback. It kind of validates my figures, which surprised me a little. I struggled with this and hope the results help others.

Vediam un po/voyons un peu/gugga mer ees/LET'S HAVE A LOOK:

standard fares for 1 pax in CHF (1 CHF = roughly 1 USD):

ZRH - Zurich (ZVV ticket, 3 zones): 7 CHF
Zurich - Grindelwald via Lucerne: 62 CHF
Zurich - Grindelwald via Berne: 81 CHF
Grindelwald - Maennlichen plus Kleine Scheidegg - Jungfraujoch - Grindelwald: 217 CHF
Grindelwald - First OW: 30 CHF
Grindelwald - Bern RT: 78 CHF
Grindelwald - Gstaad - Montbovon - Gruyeres - Bulle - Gruyeres - Montbovon - Montreux: 159 CHF
Montreux - Lausanne RT (Mobilis Day Pass, 7 zones): 26 CHF

Total via Lucerne: 579 CHF/pax resp 1158 CHF for 2 pax (1172 UDS at the actual rate)
Total via Berne: 598 CHF/pax resp. 1196 CHF for 2 pax (1211 USD at the actual rate)

The costs will be higher if you go twice to Kleine Scheidegg (once for Jungfraujoch and once for Maennlichen) or if you visit Gruyeres from Montreux (as you obviously planned).
We introduced Bulle in your itinerary because you cannot deposit your luggage at Gruyeres.

The same with Swiss Half Fare Card:
via Lucerne: 820 CHF or 830 USD for 2 pax
via Berne: 840 CHF or 850 USD for 2 pax

The same with Swiss Travel Pass:
513 + 160 + 15 = 690 CHF/pax x 2 = 1380 CHF or 1400 USD/2 pax

pro memoria: 1200 USD for point to point tickets