If you bought the train tickets through Rail Europe, then they don't offer you a choice of stations in Interlaken but your ticket is valid to either station. The computer named Interlaken West assuming that you'd want the shortest ride but you can definitely stay on the train until Interlaken Ost.
To see train schedules in Europe (but not to buy most tickets), the Deutsche Bahn link at Looking Up Train Schedules and Routes Online is very comprehensive. Of course, they get all the Swiss coordinated transport info from SBB and the rest from other national railways.
Train and lift prices around the Lauterbrunnen Valley are on the schematic on p. 129 of Rick Steves' Switzerland and at https://www.jungfrau.ch/shop/en/tickets/bergbahn. The one-month Swiss Half-Fare Card for visitors costs a relatively small investment of 120 Swiss Francs to buy there and saves money if your transport tickets would otherwise add up to at least 240 CHF. You may not rack up that much expense if only heading to mid-elevation trailheads and covering more ground with your feet.
But if you use lifts all the way from Lauterbrunnen to the top of Schilthorn and return, then it typically costs 105-113 CHF roundtrip. From Lauterbrunnen all the way to Jungfraujoch roundtrip costs 190 CHF. There may be discounts for the first couple of early-morning departures. Or tickets are cheaper if you plan to hike part of the way back downhill. I highly recommend Mt. Schilthorn for the 360-degree panoramic view, but have not gone to the Jungfraujoch, which takes longer, as well as being more expensive.
Despite Tim's frustration with Eurail, I don't think we can blame them for the relative prominence of larger towns versus small villages on maps, the general enthusiasm of the Swiss Tourist Office, or the fame that Interlaken gained as a tourist destination in the 19th century.