just wonder if Swiss citizens - not residents - get a break on the Jungfrau train?

any discounts ever available to locals?

One way to cut the costs a bit is to hike part way down - from the last station before Kleine Schiedegg to there and then walk down from there to Wengen - a sweet nice gently descending walk I did in a few hours. Probably would not save that much however as I think Kl Scheidegg to the top is the steepest train fare in the world.

No discounts to locals beyond villages inhabited all the year round.
Most people living in Switzerland have a Half Fare Card for one year or a "Generalabonnement" (similar to Swiss Pass) for 1 year and pay half fare for the Jungfrau railway.
The train ride to Jungfraujoch is a must for people who want to hike down the glaciers to Fiescheralp (usually sleeping at Konkordia Hut) or who want to cross the Loetschenluecke by ski (very popular high mountain spring ski tour up to Loetschental).

Yes of course I should have thought of the Half-Fare Card - 50% off is a lot better than 25% off.