From Rick's rail pass guide:
"The Berner Oberland Pass, like a flexipass for the Bern-Interlaken-Luzern area, is the most useful of Switzerland's regional passes. You can choose any 5 days of free travel plus 10 days of 50% discounts in a 15-day period for 277 SF ($277) second class or any 3 free days plus 4 days of 50% discount in 7 days for 230 SF ($230). The highest mountain lifts are either 50% off during the validity of the pass or have special prices (e.g., Kleine Scheidegg to the Jungfraujoch, or Murren to the Schilthorn are 50% off). Also available in first class for 20% more; or if you have any type of Swiss Pass or discount card, all prices are 20% less. To see a map of discounted rides, go to www.regiopass-berneroberland.ch. Depending on exchange rates, the full-country Swiss passes purchased before you go can be a better value."
With the pass you will still have to pay for the high mountain lifts/train, but you get a substantial discount. You should also check out the Swiss Pass, it will cover all inter/intra city transport throughout Switzerland (rail, bus,boat, cable car), free entry to most museums, and still gets you the discounts to the high mountain attractions. Click the "railpasses" tab at the top of this page for more details.