You can save francs as you get around the Bernese Oberland with the Berner Oberland Regional Pass, which allows unlimited travel on most trains, buses, boats, mountain railways and cable cars, as well as discounts on local sights and attractions (for instance, a 50% reduction on tickets to Jungfraujoch). The Junior Card (Sfr30) allows kids to travel free with their parents; unaccompanied, they pay half-price.
A good alternative is the Jungfrau Travel Pass, which provides three to six days of unlimited regional travel, though you still have to pay Sfr61 from Eigergletscher to Jungfraujoch.
Staying in local accommodation entitles you to a Gästekarte (Guest Card), good for discounts throughout the entire region. Ask your hotel for the card if one isn’t forthcoming.