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 - $23.75
Near Mint Non-English - $23.75
Lightly Played - $22.75
Lightly Played Non-English - $22.75
Moderately Played - $19.00
Moderately Played Non-English - $19.00
Heavily Played - $14.25
Heavily Played Non-English - $14.25
Damaged - $12.00
Damaged Non-English - $12.00