Shared Cab to Lachung/Lachen

I am planning a trip to sikkim with one of my friend . we both have already been to gangtok once but we want to revisit to explore offset locations like lachung, lachen . I did a bit of research and found out that a cab to lachung or lachen or lachen will cost around 11k for 1N2D. as its just two of us this is very expension. Are shared cab available like they are for siliguri to gangtok.? also if not , any offbeat location in sikkim which we can go to in lesser price?