hi there,
Here are some cheap hostels in Hawaii:
Waikiki Beachside Hostel which is a the largest hostel in Hawaii with over 100 beds. Also, it's not far at all from Waikiki Beach.
Hilo Bay Hostel which is located in downtown
Hilo outside the main road.
Paumalu Hale
Hostel located in front of Rocky Point and close to the beach also.
Hope this helps
Vacationbuddy