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
Lightly Played - $16
Moderately Played - $14
Heavily Played - $12
Damaged - $10
Near Mint Spanish - $20
Lightly Played Spanish - $16
Moderately Played Spanish - $14
Heavily Played Spanish - $12
Damaged Spanish - $10