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 - $24.70
Near Mint Non-English - $24.70
Lightly Played - $22.20
Lightly Played Non-English - $22.20
Played - $17.30
Played Non-English - $17.30
Heavily Played - $14.80
Heavily Played Non-English - $14.80
Damaged - $12.40
Damaged Non-English - $12.40