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.)
"Hup, two, three, four, Dunno how to count no more." —Mogg march
Near Mint - $33.60
Near Mint Non-English - $33.60
Lightly Played - $30.20
Lightly Played Non-English - $30.20
Played - $23.50
Played Non-English - $23.50
Heavily Played - $20.20
Heavily Played Non-English - $20.20
Damaged - $16.80
Damaged Non-English - $16.80