The budget depends on the number of ppl travelling, place of origin n mode of transport. I went on a solo trip from Chennai to Meghalaya and the total budget including flight for 5 day trip came to around 30000/-. The mode of transport locally is share taxi. since I took a taxi on my own, the local transportation alone came to around 10k for 4 days. flight cost around 12k roundtrip. stay in Shillong and cherra cost close to 7k. food cost around 1k. hope this is helpful.
I can Help you to the sikkim trip .
its around 15,000 per head .
you will get to visit Gangtok , north sikkim , east sikkim .
And the stay u will get 6 nights / 7 DAYS