From Gstaad train to Zweisimmen, train to Spiez, then train to Interlaken West. 2 h 14 min SFr 35. From Gstaad taxi to Interlaken. 1 h 8 min SFr 414. From Gstaad drive to Interlaken. 1 h 8 min SFr 10.
No, there is no direct train from Gstaad to Interlaken. However, there are services departing from Gstaad and arriving at Interlaken West via Zweisimmen and Spiez. The journey, including transfers, takes approximately 2 h 14 min.