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 - $18.75
Near Mint Non-English - $18.75
Lightly Played - $18.00
Lightly Played Non-English - $18.00
Moderately Played - $15.00
Moderately Played Non-English - $15.00
Heavily Played - $11.50
Heavily Played Non-English - $11.50
Damaged - $9.50
Damaged Non-English - $9.50