Is there any alternative to go to kamand campus, IIT Mandi in the night at 2 AM other than hiring taxi worth ?800?

No, there is no other alternative than hiring a taxi at 2 a.m. since the last bus to Kamand is around 9:30 p.m. But hiring a taxi for INR 800 is expensive; you can bargain until the price cuts to around INR 500, and this is not an easy task since the taxi drivers charge high at night. 

Usually, the students chose HRTC (the bus service offered by the government) to reach the Kamand campus. The first bus to Kamand is scheduled for 6 a.m., and the bus starts from the HRTC bus stand in Mandi, which is opposite the Vallabh Government College.