The phase refers to the color distribution and rarity of the pattern generated from the texture template. Phase 2 and Phase 4 are generally more expensive because they have more pink or blue, respectively. If you have a Ruby or Emerald version, the price jumps even higher into the thousands. These "Gems" are extremely rare and occupy a completely different price bracket than standard phases. The community values vibrant, solid colors much more than the dark, muddy mixes found in Phase 1 or 3. You should definitely verify the exact phase of your knife using a reliable database before accepting any offers