Accommodation is expensive in Stockholm. You may plan well to save money. Normal hotel may cost you from 100$ to 250 $ per night. Here are some tips which can make your stay in Stockholm at budget.
Stay at Hostel: It may surprise you, but it is the best way to save your money. Per night may cost you around 20$ in most of these hostels.
Hotel Point: If you got hotel points, would book any famous international hotel in the city which would definitely save your money.
Hospitality Network: Connect to a hospitality network (i.e. Couchsurfing) where you may meet locals who offers free accommodations plus you get a chance to learn local culture and can make some friends as well.