Cheapest priced copy (Ice Age): $0.35 at Card Kingdom, near mint, their price list as of .
Aurochs 
Creature — Aurochs · 2/3 · Common · Fifth Edition · #279
Trample
Whenever this creature attacks, it gets +1/+0 until end of turn for each other attacking Aurochs.
Legal inCommanderLegacyVintagePauper
Not legal inBrawlStandardPioneerModern
3 printings · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Fifth Edition | 279 | Common | $0.49 | — |
| Coldsnap Theme Decks | 225 | Common | $0.49 | — |
| Ice Age | 225 | Common | $0.35 | — |
2 rulings from Wizards of the Coast
- 4 October 2004The bonus is not applied until after you check for attack legality, so it is a 2/3 creature when declaring attackers.
- 1 October 2009The ability counts the number of attacking creatures with the creature type Aurochs, not just those named Aurochs.