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 - $25.25
Near Mint Non-English - $25.25
Lightly Played - $24.00
Lightly Played Non-English - $24.00
Moderately Played - $20.25
Moderately Played Non-English - $20.25
Heavily Played - $15.25
Heavily Played Non-English - $15.25
Damaged - $12.75
Damaged Non-English - $12.75