Each creature gets +1/+1 for each other creature on the battlefield that shares at least one creature type with it. (For example, if two Goblin Warriors and a Goblin Shaman are on the battlefield, each gets +2/+2.)
Near Mint - $24.50
Near Mint Non-English - $24.50
Lightly Played - $22.10
Lightly Played Non-English - $22.10
Played - $17.20
Played Non-English - $17.20
Heavily Played - $14.70
Heavily Played Non-English - $14.70
Damaged - $12.30
Damaged Non-English - $12.30