Let KAYAK do the searching
Based on KAYAK hotel searches, the most popular destination is Medan (70% of total searches to North Sumatra). The next most popular destinations are Parapat (14%) and Berastagi (12%). Searches for hotels in Pematangsiantar (3%) are also popular.
KAYAK users have found double rooms in North Sumatra for as cheap as $7 (Siborong-Borong) in the last 3 days. The average price is $57.