Good hash is made from the strongest part of the marijuana plant. It is filtered through a very dense screen so that only the pure crystals can pass through. These crystals are compressed to make hash. You need several ounces of good marijuana to produce a couple of grams of good hash. That's why it is so expensive. The quality of the hash all comes from the quality of the buds it was made with and how finely it is filtered or sifted.