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 - $20.90
Near Mint Non-English - $20.90
Lightly Played - $18.90
Lightly Played Non-English - $18.90
Played - $14.70
Played Non-English - $14.70
Heavily Played - $12.60
Heavily Played Non-English - $12.60
Damaged - $10.50
Damaged Non-English - $10.50