Hello, I am from Uttarakhand and it can cost you Minimium 2000- 4000 depend on your commute as now in north India you don't have to travel by AC bus you can go by normal bus and change bus from Rishikesh.
It should cost you around 20K. Including cab rent/fuel cost,interstate permit, and accomodation. Hotels in the Lansdowne valley are cheaper and also provide riverside camping options. This being a relatively off-season should give you a scope of bargaining if you book (in advance, ofcourse) directly or availing discounts for online booking.